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EXPERIMENTAL  VEGETATION 


THE  RELATION  OF  CLIMAXES  TO  CLIMATES 


BY 

Frederic  E.  Clements  and  John  E.  Weaver 


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Published  by  the  Carnegie  Institution  of  Washington 
Washington,  December,  1924 


CARNEGIE  INSTITUTION  OF  WASHINGTON 
Publication  No.  355 


Judd  &  Detweiler,  Inc. 

WASHINGTON,  D.  C. 


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CONTENTS. 


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FAGE. 

List  of  illustrations .  v 

1.  Introduction. 

Scope  and  plan .  3 

Principles .  3 

Methods.... .  4 

Values .  5 

The  grassland  climax .  5 

Tests  of  unity .  6 

Further  evidence .  7 

Relationship  of  the  associations . . . 


Climatic  unity .  8 

Objectives  of  the  present  investigation  9 

Stations .  10 

Location .  10 

True-prairie  stations .  11 

Mixed-prairie  station .  12 

Plains  station .  13 

Physical  factors .  15 

Rainfall  and  holard .  15 

Temperature .  17 

Wind  and  evaporation .  18 

Detailed  methods .  21 

Germination  of  seed .  21 

Depth  of  planting .  21 

Methods  of  sowing  and  planting . .  23 

.  Experiments  During  1920  .  27 

High  prairie,  Lincoln .  27 

Surface  sowing .  27 

Trench  sowing .  27 

Quadrat  sowing .  27 

Root  habits  of  seedlings .  29 

Summary  of  planting  results .  31 

Sod  transplants .  31 

Mixed  prairie,  Phillipsburg .  31 

Surface  sowing .  31 

Trench  and  quadrat  sowing .  33 

Short-grass  plains,  Burlington .  33 

Surface  sowing .  33 

Trench  and  quadrat  sowing .  33 

Sod  transplants .  34 

Summary  of  experiments .  34 

Seeding  in  cultivated  areas  at  all 

stations .  35 

True  prairie .  35 

Root  development .  35 

Mixed  prairie  and  short-grass 

plains .  36 

Experiments  at  other  climatic  stat  ions.  36 
Subclimax  prairie,  Nebraska  City.  36 

Character .  36 

Results .  38 

Mixed  prairie,  Colorado  Springs .  .  39 

Character .  39 

Results .  39 

Experiments  at  edaphic  stations. .  40 

Gravel-knoll  station .  40 

Character .  40 


iii 


PAGE. 


2.  Experiments  During  1920. — Cont. 

Gravel-knoll  station — Cont. 

Behavior .  41 

Low-prairie  station .  42 

Character .  42 

Behavior .  43 

Salt-flat  station .  44 

Character .  44 

Behavior .  45 

Swamp  station .  45 

Character .  45 

Behavior .  46 

Summary .  47 

Experiments .  47 

Physical  factors .  48 

Experiments  during  1918  and  1919. .  49 

Season  of  1918 .  49 

Season  of  1919 .  50 

Sod  transplants .  51 

Gravel-knoll .  51 

Low  and  high  prairie .  52 

Mixed  prairie .  55 

3.  Experiments  During  1921 .  56 

Physical  factors .  56 

Rainfall .  56 

Water  relations .  56 

Temperature .  59 

Planting  results .  60 

Surface  sowing .  60 

Trench  sowing . .  60 

Denuded  quadrats .  61 

Root  development  in  denuded 

quadrats . 63 

Seedling  transplants .  65 

Summary .  65 

Sod  transplants .  66 

Root  development .  67 

Experiments  at  other  stations,  1921.  70 

Physical  factors .  70 

Rainfall  and  holard .  70 

Evaporation  and  temperature.  .  71 

Planting  results .  71 

Surface  sowing .  71 

Trench  sowing .  74 

Growth  in  cultivated  soil .  75 

Root  development  at  Lincoln. . .  76 

Sowing  in  denuded  quadrats.  .  .  78 

Root  development  at  Peru, 

Nebraska .  80 

Seedling  transplants .  80 

Summary .  81 

Sod  transplants .  83 

Gravel-knoll .  83 

Low  prairie .  84 

Salt-flat .  85 

Salt-basin .  86 

Swamp .  86 

Regional  transplants .  88 


568008 


IV 


CONTENTS. 


PAGE. 


4.  Experiments  During  1922 .  89 

Physical  factors .  89 

Rainfall .  89 

Holard .  89 

Temperature .  89 

Humidity .  91 

Evaporation .  92 

Planting  results .  92 

Surface  sowing .  92 

Trench  sowing .  93 

Denuded  quadrats .  95 

Summary .  96 

Seedling  transplants .  97 

Summary .  98 

Sod  transplants .  98 

Experiments  at  other  stations,  1922 .  99 

Physical  factors .  99 

Water  relations .  99 

Planting  results .  101 

Surface  sowing .  101 

Trench  sowing .  102 

Denuded  quadrats .  102 

Seedling  transplants .  103 

Effect  of  competition .  104 

Summary .  105 

Sod  transplants. .  105 

5.  Experiments  During  1923 .  109 

Development  of  seedlings  and  trans¬ 
plants .  109 

Physical  factors .  109 

Water  relations .  109 

Survival  results .  110 

Surface  sowing .  Ill 

Trench  sowing .  Ill 

Denuded  quadrats .  112 

Seedling  transplants .  112 

Experiments  at  edaphic  stations. ...  112 

Survival  results .  112 

Surface  sowing .  112 

Trench  sowing .  113 

Denuded  quadrats .  113 

Seedling  transplants .  113 

Summary  of  survival .  113 

Sod  transplants .  115 

Phytometric  results .  116 

Transpiration  and  growth . '  116 

Plan .  116 

Methods .  116 

Conditions  and  results  at  Lin¬ 
coln .  117 

Physical  factors .  117 

Transpiration  and  increase  in 

leaf-area .  119 

Conditions  and  results  at  Phil- 

lipsburg .  119 

Installation .  119 

Physical  factors .  119 

Transpiration  and  increase  in 
leaf-area .  120 


page. 

5.  Experiments  During  1923 — Cont. 
Phytometric  results — Cont. 

Conditions  and  results  at  Bur¬ 


lington .  119 

Installation .  119 

Physical  factors .  121 

Transpiration  and  increase  in 

area .  121 

Summary  and  conclusions .  123 

Transpiration  and  growth  of 

communities .  123 

Transpiration  from  natural 

cover  and  crops .  123 

Objectives .  123 

Methods .  124 

True  prairie,  series  1 .  125 

Installation . . .  125 

Results .  126 

True  prairie,  series  2 .  126 

Installation .  126 

Results .  127 

Mixed  prairie .  127 

Installation .  127 

Results .  128 

Short-grass  plains .  128 

Installation .  128 

Results .  129 

Summary .  130 

Growth  of  natural  cover  and  crops.  131 

Objectives .  131 

Plan .  131 

Results  for  1920 .  132 

Results  for  1921 .  133 

Results  for  1922 .  135 

Results  for  1923 .  136 

Summary . .  136 

Structural  reponse  of  dominants 

and  subdominants .  137 

Scope  and  significance .  137 

6.  R£sum£ .  138 

Plan  and  methods .  138 

Communities .  139 

Physical  factors  for  1920 .  140 

Ecesis  during  1920 .  140 

Physical  factors  for  1921 .  141 

Ecesis  during  1921 .  142 

Physical  factors  for  1922 .  142 

Ecesis  during  1922 .  143 

Behavior  during  1923 .  144 

Behavior  of  trees  and  shrubs .  146 

Germination  and  survival  at  the  cli¬ 
matic  stations .  147 

Germination  and  survival  at  the 

edaphic  stations .  148 

Survival  of  sod  transplants .  151 

Phytometric  methods .  151 

Attainment  of  objectives .  152 

Bibliography .  154 

Behavior  tables .  155 


LIST  OF  ILLUSTRATIONS. 


PLATES. 

Plate  1. 

A.  Detail  of  high  prairie,  showing  the  luxuriant  estival  society  and  the  amount 

of  forage  produced  in  June. 

B.  General  view  of  high  prairie  at  Lincoln,  Nebraska . 

Plate  2. 

A.  Mixed-prairie  station  at  Phillipsburg,  Kansas . 

B.  Corner  of  short-grass  plains  station  at  Burlington,  Colorado. 

Plate  3. 

Root  system  of  year-old  Andropogon  scoparius  ( A )  and  Stipa  viridula  (B),  upland 
cultivated  soil  at  Lincoln;  maximum  penetration  4  and  2.7  feet  respectively . 

Plate  4. 

Year-old  Elymus  canadensis  (A),  Bouteloua  racemosa  (B),  and  Andropogon  nutans 
( C ) ;  maximum  penetration  about  3,  3,  and  4  feet  respectively . 

Plate  5. 

A.  Gravel-knoll  station,  Lincoln . 

B.  Low-prairie  station,  Lincoln,  showing  transplanted  sods. 

Plate  6. 

A.  Low-prairie  station  in  September  showing  height  of  the  subclimax  dominants . 

B.  Salt-flat  station,  Lincoln;  the  chief  grass  is  Distichlis  spicata. 

Plate  7. 

A.  View  of  sod  transplants  in  the  swamp  at  Lincoln,  showing  water  standing  on  the 

surface. 

B.  Subclimax  prairie  at  Nebraska  City,  showing  rank  growth  of  Stipa  spartea 

and  Ceanothus  ovatus  held  in  check  by  mowing. 

Plate  8. 

A.  A  single  season’s  growth  of  Andropogon  nutans  from  block  of  sod  (left)  and  from 

seed  (right)  on  low  prairie  at  Lincoln . 

B.  Year-old  Bouteloua  hirsuta  grown  on  high  prairie  at  Lincoln. 

Plate  9. 

A.  Year-old  seedlings  of  Andropogon  scoparius  (right),  A.  nutans  (center),  and  A. 

furcatus  (left)  grown  on  high  prairie;  plants  about  6-8  inches  tall . 

B.  Root  system  of  year-old  Andropogon  furcatus  from  cultivated  lowland,  Lincoln; 

scale  in  feet . 

Plate  10. 

A.  Bulbilis  dactyloides  sod  in  high  prairie. 

B.  Andropogon  nutans  in  September  of  first  season,  showing  marked  growth  with¬ 

out  competition. 

Plate  11. 

A.  Calamovilfa  longifolia  in  September  of  first  season,  grown  in  rich  silt-loam. 

B.  Bouteloua  gracilis  one  year  old,  grown  in  cultivated  soil . 

Plate  12. 

Roots  of  year-old  Muhlenbergia  pungens  (A)  and  Calamovilfa  longifolia  (B)  grown 
in  rich  silt-loam;  depths  of  penetration  2.5  and  6  feet  respectively. 

C.  Andropogon  halli  at  the  end  of  the  first  year  in  silt-loam . 

Plate  13. 

Andropogon  nutans  planted  in  denuded  quadrats  at  Nebraska  City,  (A)  in  1922, 
(B)  in  1920;  photographed  June  3,  1922. 

Plate  14. 

A.  Two-year-old  Liatris  punctata  (left)  and  L.  scariosa  (right)  grown  without  com¬ 

petition  in  cultivated  soil:  the  largest  plant  had  107  heads. 

B.  Year-old  Desmodium  canescens  and  two-year-old  Onagra  biennis  ( C )  growm  in 

cultivated  soil  at  Lincoln;  maximum  heights  5  and  7  feet  respectively. 

Plate  15. 

A.  Sod-cores  and  details  of  installation,  Burlington. 

B.  Clip-quadrat  in  Bulbilis-Bouteloua  short-grass,  Burlington. 


v 


VI 


LIST  OF  ILLUSTRATIONS. 


TEXT-FIGURES.  page. 

1.  Map  showing  location  of  stations  in  the  four  grassland  communities .  10 

2.  Mean  annual  precipitation  at  Lincoln  (solid  line),  Phillipsburg  (long  broken 

lines),  and  Burlington  (short  broken  lines) .  15 

3.  Average  daily  temperature  at  Lincoln  (solid  line),  Phillipsburg  (long  broken 

lines)  and  Burlington  (short  broken  lines),  1920;  here,  as  elsewhere, 
the  numbers  denote  the  first,  second,  third,  or  fourth  week  in  the  month, 
respectively .  17 

4.  Average  day  (heavy  lines)  and  night  temperatures  (light  lines),  at  Lincoln  (solid 

lines),  Phillipsburg  (long  broken  lines),  and  Burlington  (short  broken 
lines),  1920 .  17 

5.  Average  daily  soil-temperatures  at  Lincoln  (solid  line),  Phillipsburg  (long 

broken  lines),  and  Burlington  (short  broken  lines),  1920 .  18 

6.  Hvgrothermograph  records  from  Lincoln  (upper)  and  Burlington  (lower), 

June,  1921;  light  lines  temperature,  heavy  lines  humidity .  19 

7.  Average  day  (light  lines)  and  night  humidity  (heavy  lines)  at  Lincoln  (solid 

lines),  and  Burlington  (broken  lines),  1920 .  20 

8.  Average  daily  evaporation  at  Burlington  (short  broken  lines),  Phillipsburg 

(long  broken  lines),  and  Lincoln  (solid  line),  1920 .  20 

9.  Monthly  precipitation  at  Lincoln  1920-1922;  the  monthly  mean  is  shown  by 

the  heavy  cross-bars .  27 

10.  Plants  of  Bouteloua  gracilis  (A),  Bouteloua  hirsuta  ( B ),  and  Sporobolus  asper 

( C )  44-days  old;  scale  1  foot .  28 

11.  Bouteloua  gracilis  3  months  old .  29 

12.  Bouteloua  hirsuta  3  months  old .  29 

13.  Stipa  spartea  3  months  old .  30 

14.  A gropyrum  glaucum  3  months  old .  30 

15.  Monthly  precipitation  at  Phillipsburg  1920-1922;  the  monthly  mean  is  shown  . 

by  the  heavy  cross-bars .  32 

16.  Monthly  precipitation  at  Burlington  1920-1922,  the  monthly  mean  is  shown 

by  the  heavy  cross-bars .  32 

17.  Root  of  Liatris  punctata  at  end  of  first  season’s  growth .  35 

18.  Monthly  precipitation  at  Nebraska  City  1920-1922;  the  monthly  mean  is 

shown  by  the  heavy  cross-bars . 37 

19.  Average  daily  evaporation,  high  prairie  (solid  line),  and  low  prairie,  Lincoln 

(short  broken  lines),  and  Nebraska  City  (long  broken  lines),  1920. ....  48 

20.  Average  daily  evaporation  on  high  prairie  (upper  line)  and  low  prairie  (lower 

line),  1920 . 52 

21.  Average  day  and  night  temperatures  at  Lincoln  (solid  lines),  and  Colorado 

Springs  (broken  lines),  during  1919 .  53 

22.  Average  daily  evaporation  at  Colorado  Springs  (upper  line),  and  Lincoln 

(lower  line),  during  1919 .  54 

23.  Average  daily  evaoraption  at  Burlington  (short  broken  lines),  Phillipsburg 

(long  broken  lines),  and  Lincoln  (solid  line),  1921 .  56 

24.  Average  daily  temperature  at  Lincoln  (solid  line),  Phillipsburg  (long  broken 

lines),  and  Burlington  (short  broken  lines),  1921 .  57 

25.  Average  day  (heavy  lines)  and  night  temperatures  (light  lines),  at  Lincoln 

(solid  lines),  Phillipsburg  (long  broken  lines),  and  Burlington  (short 
broken  lines),  1921 .  59 

26.  Average  daily  soil  temperatures  at  depths  of  3  and  18  inches  respectively  at 

Lincoln  (solid  line),  Phillipsburg  (long  broken  lines),  and  Burlington 
(short  broken  lines),  1921 .  62 

27.  Liatris  punctata  from  Phillipsburg,  on  July  1  of  second  year  after  planting.  ...  63 

28.  Bouteloua  hirsuta  from  Phillipsburg,  on  July  1  of  second  year  after  planting. . .  63 

29.  Andropogon  scoparius  from  Phillipsburg,  on  July  1  of  second  year  after  planting.  64 

30.  Roots  of  Andropogon  nutans  after  the  block  of  sod  had  been  transplanted  for 

2.5  months  at  Burlington .  64 

31.  Roots  of  Elymus  canadensis  at  the  end  of  June  of  the  second  year  after  the 

block  of  sod  had  been  transplanted  and  watered  at  Burlington .  64 


LIST  OF  ILLUSTRATIONS. 


VII 


TEXT-FIGURES — Continued.  page. 

32.  Roots  of  Panicum  virgatum  at  the  end  of  June  of  second  year  after  the  block 

of  sod  had  been  transplanted  and  watered  at  Burlington .  69 

33.  Average  daily  evaporation  on  high  prairie  (solid  line),  gravel-knoll,  Lincoln 

(short  broken  lines),  and  at  Nebraska  City  (long  broken  lines),  1921 . .  71 

34.  Pinus  ponderosa  2.5  months  old .  76 

35.  Liatris  punctata  2.5  months  old .  76 

36.  Robinia  pseudacacia  2.5  months  old .  77 

37.  Root  system  of  Gleditsia  triacanthus  less  than  3  months  old .  78 

38.  Average  daily  temperatures  at  Lincoln  (solid  line),  Phillipsburg  (long  broken 

lines),  and  Burlington  (short  broken  lines),  1922 .  91 

39.  Average  day  (heavy  lines)  and  night  temperatures  (light  lines)  at  Lincoln 

(solid  line),  Phillipsburg  (long  broken  lines),  and  Burlington  (short 
broken  lines),  1922 .  92 

40.  Average  daily  soil  temperatures  at  depths  of  3  and  12  inches  respectively  at 

Lincoln  (solid  line),  Phillipsburg  (long  broken  lines),  and  Burlington 
(short  broken  lines),  1922 .  93 

41.  Average  daily  evaporation  at  Lincoln  (solid  lines),  Phillipsburg  (long  broken 

lines),  and  Burlington  (short  broken  lines),  1922 .  94 


' 


. 


EXPERIMENTAL  VEGETATION 


THE  RELATION  OF  CLIMAXES  TO  CLIMATES 


BY 

Frederic  E.  Clements 
and 


John  E.  Weaver 


EXPERIMENTAL  VEGETATION. 


1.  INTRODUCTION. 

SCOPE  AND  PLAN. 

The  investigations  that  have  led  to  the  development  of  the  phytometer 
and  the  experimental  method  in  vegetation  are  companion  efforts  in  the  en¬ 
deavor  to  organize  ecology  as  a  quantitative  science.  No  subject  has  suf¬ 
fered  more  from  the  lack  of  training  and  experience  or  from  the  absence  of 
basic  procedure  and  adequate  perspective.  It  has  become  obvious  that  this 
condition  can  be  remedied  and  actual  progress  insured  only  by  instrumental 
and  experimental  methods  and  by  a  combination  of  intensive  and  extensive 
studies  that  will  check  superficiality  on  the  one  hand  and  broaden  limited 
horizons  on  the  other.  It  is  certain  that  much  work  of  purely  superficial  or 
local  character  will  continue  to  be  done  under  the  name  of  ecology,  but  the 
touchstones  of  instrument,  quadrat,  and  experiment  afford  a  ready  means  of 
eliminating  such  papers  from  consideration.  No  study  deserves  to  be  called 
ecological  that  does  not  deal  with  the  cause-and-effect  relation  of  habitat  and 
organism  in  a  quantitative  and  objective  manner. 

The  task  of  focusing  the  efforts  of  the  ecologist  upon  the  habitat  as  cause 
and  the  plant  and  community  as  effect  and  reaction  furnishes  the  theme  for 
four  related  studies,  namely,  phytometers,  experimental  vegetation,  climatic 
cycles,  and  changes  of  climate  and  climax.  The  first  two  constitute  an 
endeavor  to  employ  plant  and  community  as  the  best  measures  of  cause  and 
reaction,  while  the  last  two  emphasize  the  fundamental  significance  of  change 
as  the  proper  approach  to  this  complex  of  problems. 

PRINCIPLES. 

The  basic  guides  in  this  task  are  the  cause-and-effect  relation  on  the  one 
hand  and  the  cyclic  nature  of  change  on  the  other.  The  former  is  paramount 
in  every  ecological  problem,  since  investigation  that  does  not  deal  directly 
and  constantly  with  causes  lacks  the  very  essence  of  science.  However,  in 
dealing  with  processes  in  a  way  that  is  at  once  complete  and  synthetic,  ecology 
must  not  overlook  the  fact  that  both  cause  and  effect  must  be  inseparably 
associated  and  that  effect  sometimes  affords  the  readier  approach  to  the  prob¬ 
lem.  It  is  equally  essential  that  ecology  be  treated  as  inherently  dynamic, 
that  change  in  some  degree  or  at  some  rate  be  regarded  as  universal,  and  that 
such  changes  be  recognized  as  recurrent  or  cyclic,  both  as  cause  and  in  effect. 
The  fact  has  elsewhere  been  emphasized  that  effects  in  turn  produce  reactions, 
which  consequently  become  causal  to  the  extent  that  they  modify  the  original 
causes  (Plant  Succession,  79).  This  constitutes  the  basic  cycle  which  finds 
its  expression  in  the  larger  cycle  of  the  sere.  Thus,  succession  is  an  intrinsic 
function  of  all  vegetation,  though  the  shifting  of  climaxes  is  a  matter  of  thou¬ 
sands  or  tens  of  thousands  of  years  rather  than  of  scores  in  the  subsere  or 
hundreds  in  the  prisere. 


3 


4 


INTRODUCTION. 


The  cyclic  changes  of  the  habitat  are  likewise  reflected  in  the  individual  and 
the  species.  Adjustment  and  adaptation  are  clearly  cyclic  processes,  and 
this  is  even  more  evident  in  the  major  evolutions  of  groups  and  floras.  As 
the  consequence  of  reaction  and  competition  in  the  sere  and  of  climatic  shift 
in  the  major  seres,  invasion  is  necessarily  cyclic  and  finds  its  typical  expression 
in  terms  of  dominant  and  relict  phases.  Finally,  cyclic  changes  serve  to 
link  the  present  with  the  past  in  such  a  broadly  continuous  fashion  that  the 
gap  between  them  disappears  and  such  terms  as  ecology  and  paleo-ecology 
are  seen  to  be  mere  conveniences. 

METHODS. 

The  methods  of  experimental  vegetation  are  based  on  the  processes  inher¬ 
ent  in  the  natural  development  of  vegetation,  but  segregated  and  controlled 
in  such  a  way  as  to  reveal  the  value  and  significance  of  each  individual  step 
or  process.  This  is  even  true  of  migration,  regarded  merely  as  transport, 
the  difference  in  the  role  of  man  as  an  unintentional  or  purposeful  agent  being 
immaterial,  except  as  to  the  number  and  fate  of  the  migrules.  The  most 
exact  evidence  as  to  the  nature  and  success  of  invasion  and  ecesis  is  doubtless 
that  to  be  obtained  in  the  form  of  natural  experiments,  but  except  in  the  case 
of  propagules  these  are  difficult  to  discover  outside  of  ecotones  and  are  alto¬ 
gether  absent  from  the  typical  areas  of  great  associations.  Hence,  the  only 
feasible  procedure  is  to  approximate  the  method  of  natural  experiment  as 
closely  as  possible,  bearing  in  mind  that  the  numbers  must  be  large  enough 
to  insure  against  complete  loss.  Moreover,  it  must  be  recognized  that  arti¬ 
ficial  aids  to  ecesis,  such  as  watering,  screening,  etc.,  fall  well  within  the  vari¬ 
ation  of  factors  in  nature  and  are  in  consequence  more  or  less  natural. 

The  basic  methods  of  experimental  vegetation  are  as  follows:  (1)  sowing 
seeds;  (2)  planting  seeds  or  propagules;  (3)  planting  seedlings;  (4)  transplant¬ 
ing  adult  plants  of  various  ages;  (5)  transplanting  small  communities  or  por¬ 
tions  of  communities.  The  converse  of  this  is  to  be  found  in  the  method  of 
denuded  quadrats  and  transects,  but  as  this  is  primarily  a  question  of  ecesis 
within  a  community,  it  has  not  been  extensively  employed  in  the  present 
study.  The  accessory  methods  involve  the  use  or  manipulation  of  (1)  com¬ 
petition;  (2)  physical  factors;  (3)  protection  against  animals;  (4)  instruments; 
(5)  phytometers;  (6)  seasons  and  cycles.  Time  also  enters  the  equation,  inas¬ 
much  as  germination  and  the  ecesis  of  seedlings  are  periods  of  the  greatest 
stress.  Various  ways  are  available  for  reducing  or  eliminating  competition 
and  modifying  the  physical  factors,  but  the  following  have  proved  the  sim¬ 
plest  and  most  satisfactory,  viz:  (1)  sowing  on  the  surface  in  the  midst  of 
natural  vegetation;  (2)  sowing  or  planting  in  trenches,  by  which  competition 
is  prevented  for  a  short  time;  (3)  sowing  or  planting  in  denuded  quadrats, 
which  eliminates  competition  for  a  much  longer  period,  but  renders  the  water 
relations  usually  less  favorable  at  the  same  time  that  it  improves  light  con¬ 
ditions;  (4)  transplanting  adult  plants  into  living  cover  or  denuded  areas, 
with  similar  consequences  as  to  competition,  water,  and  light;  (5)  improving 
the  conditions  for  germination,  establishment,  or  survival  by  watering,  shad¬ 
ing,  thinning,  draining,  etc.  A  full  battery  of  recording  instruments  is  indis¬ 
pensable  and  must  be  supplemented  by  determinations  of  chresard,  evapora¬ 
tion,  and  light  intensity  in  all  cases,  and  of  salts  and  air-content  whenever 


GRASSLAND  CLIMAX. 


5 


these  are  controlling.  Equally  essential  are  phytometers  of  various  types 
to  serve  as  interpreters  between  the  physical  instruments  and  the  natural 
cover  on  the  one  hand,  and  the  transplants  on  the  other.  Furthermore,  the 
differences  between  seasons  and  the  wet  and  dry  phases  of  the  climatic  cycle 
must  be  taken  into  definite  consideration,  as  they  are  often  greater  than  the 
climatic  differences  between  the  several  grassland  associations  or  even  between 
formations.  Finally,  a  clear  distinction  must  be  drawn  between  persistence 
and  dominance,  the  former  indicating  the  potential  and  the  latter  the  actual 
role  of  a  species  in  the  climax. 

VALUES. 

The  basic  value  of  the  experimental  method  in  vegetation  is  evident,  but 
its  far-reaching  significance  warrants  detailed  consideration.  While  its  first 
importance  inheres  in  its  being  indispensable  in  the  search  for  causes,  the 
problems  of  the  origin,  unity,  and  relationship  of  formations  and  associations 
and  their  correlation  with  climate  can  be  solved  objectively  and  permanently 
in  no  other  way.  In  fact,  the  objectivity  afforded  by  comprehensive  and 
repeated  experiment  is  the  paramount  reason  for  its  constant  and  universal 
use.  The  opinions  and  hypotheses  arising  from  observation  are  often  inter¬ 
esting  and  suggestive  and  may  even  have  permanent  value,  but  ecology  can 
be  built  upon  a  lasting  foundation  solely  by  means  of  experiment.  This  does 
not  mean  that  observation  and  reconnaissance  have  no  value,  but  such  results 
are  to  be  regarded  as  provisional,  pending  adequate  experimental  study.  Still 
less  does  it  mean  that  hypothesis  and  theory  are  to  have  no  part  in  an  exact 
and  quantitative  ecology.  Such  a  view  is  possible  only  to  those  who  ignore 
the  decisive  role  that  theory  has  played  in  the  development  of  modern  chem¬ 
istry  and  physics  and  are  unfamiliar  with  its  essential  stimulus  in  the  ad¬ 
vance  of  biology. 

The  study  of  vegetation  demands  the  use  of  experiment  to  even  a  greater 
degree  than  that  of  the  plant,  owing  to  the  complexity  and  extent  of  the  great 
communities  and  the  consequent  opportunity  for  making  general  observations 
and  forming  unchecked  opinions.  Moreover,  it  must  be  fully  recognized 
that  the  intensive-extensive  method  of  investigation  applies  with  peculiar 
force  to  the  plant  community,  since  it  was  developed  for  the  express  purpose 
of  turning  complexity  and  extent  to  the  advantage  of  thorough  and  detailed 
analysis.  As  a  procedure,  it  has  been  fully  justified  by  the  experience  of 
years  in  the  vegetation  of  western  North  America,  in  which  the  extensive 
results  of  constant  field  studies  have  given  perspective  and  balance  as  well 
as  new  points  of  departure  to  the  results  of  the  laboratory  and  station,  and 
the  latter  have  served  to  refine  and  definitize  the  natural  experiments  and 
observations  over  a  vast  territory. 

THE  GRASSLAND  CLIMAX. 

The  development  of  the  views  as  to  the  nature  and  structure  of  the  grass¬ 
lands  of  North  America  illustrates  the  need  of  objective  methods  of  determin¬ 
ing  vegetation  units  and  their  relationships.  This  is  all  the  more  convincing, 
since  the  ecological  investigation  of  the  prairie  and  plains  has  been  the  work 
of  a  group  with  the  same  general  training  and  outlook.  In  the  first  analysis 
of  the  grassland,  Pound  and  Clements  (1898:243,  1900:347)  recognized  two 


6 


INTRODUCTION. 


prairie  formations,  viz,  the  prairie-grass  and  the  buffalo-grass  formations,  a 
bunch-grass  formation  of  the  sandhills,  and  a  meadow  formation.  In  the 
light  of  successional  studies,  the  last  two  are  to  be  regarded  as  subclimaxes. 
In  a  few  years  (Clements,  1902)  it  had  become  clear  that  the  prairie-grass 
or  Stipa- Agropyrum  formation  and  the  buffalo-grass  or  Bulbilis-Bouteloua 
formation  were  the  two  great  communities  of  the  prairie-plains  region. 
This  was  essentially  the  view  also  of  Shantz  (1906,  1911)  and  of  Pool  (1914). 
This  conception  was  maintained  in  Plant  Succession  (180,  cf.  note)  after 
many  additional  years  of  successional  research.  However,  the  developmental 
concept  of  the  formation  had  broadened  its  scope  and  afforded  a  clearer  view 
of  its  structure.  As  a  consequence  of  the  special  study  of  these  relations,  it 
became  necessary  to  abandon  the  view  of  two  separate  grassland  formations 
and  to  recognize  a  single  formation  composed  of  several  associations.  Mean¬ 
while,  it  had  become  increasingly  evident  that  the  Agropyrum  consociation 
of  the  Northwest  was  closely  related  to  the  Stipa-Agropyrum  prairie.  This 
was  first  suggested  by  finding  the  three  dominants  associated  from  Washing¬ 
ton  to  Montana  during  the  field  work  of  1914,  a  view  adopted  by  Weaver, 
who  had  worked  intensively  in  this  community  (1917:40).  This  idea  was 
confirmed  by  further  studies  in  1917,  but  the  true  relationship  was  obscure 
until  it  became  certain  in  1918  that  Stipa  setigera  and  S.  eminens  were  the 
original  bunch-grasses  of  California.  As  a  consequence,  it  proved  possible 
to  recognize  a  fourth  grassland  association,  composed  of  bunch-grasses  and 
characteristic  of  the  Pacific  region  of  winter  precipitation  (Plant  Indicators, 
115).  By  means  of  extensive  field  work  and  the  comparative  study  of  com¬ 
munities,  the  actual  relationship  of  the  grassland  units  was  determined,  but 
the  experimental  method  might  well  have  accomplished  in  5  years  what  obser¬ 
vation  required  20  years  to  attain. 

TESTS  OF  UNITY. 

In  reaching  the  conclusion  that  the  grasslands  constitute  a  single  climax 
formation  and  not  several  more  or  less  related  but  distinct  units,  recourse  was 
had  to  a  number  of  tests,  all  as  objective  as  possible. 

“The  conclusion  that  the  grassland  is  a  single  great  climax  formation  is  based  in 
the  first  place  on  the  fact  that  the  three  most  important  dominants,  Stipa,  Bouteloua, 
and  Agropyrum ,  extend  over  most  of  the  area,  and  one  or  the  other  is  present  in 
practically  every  association  of  it.  This  would  seem  the  most  conclusive  evidence 
possible,  short  of  actual  vegetation  experiments,  that  the  grassland  is  a  climatic  vege¬ 
tation  unit.  Equally  cogent  is  the  fact  that  these  dominants,  together  with  Carex, 
Bulbilis,  and  Koeleria,  mix  and  alternate  in  various  groupings  throughout  the  Stipa- 
Bouteloua  association.  Indeed,  this  association  appears  so  conclusive  as  to  the  gen¬ 
eral  formational  equivalence  of  these  seven  dominants  that  it  is  regarded  as  the 
typical  or  base  association.  In  addition,  the  characteristic  societies  either  extend 
through  several  of  the  associations  or  are  represented  by  corresponding  communities 
belonging  to  the  same  genus.  The  relation  of  the  associations  to  such  subclimax 
species  as  Andropogon  scoparius,  Calamovilfa  longifolia,  Aristida  purpurea,  and  Elymus 
sitanion  further  confirms  the  relationship  of  the  dominants.  The  most  obvious  differ¬ 
ence  between  the  various  associations  is  exhibited  by  the  tail-grass  prairies,  Stipa- 
Koeleria  poium ,  and  the  short-grass  plains,  Bulbilis-Bouteloua  poium.  Yet  these 
are  closely  related,  as  shown  not  only  by  the  criteria  given  above,  but  also  by  their 
geographical  contact.  Still  more  eloquent  is  the  fact  that  grazing  favors  Bouteloua 
and  Bulbilis  at  the  expense  of  Stipa  and  Agropyrum,  and  thus  frequently  converts  the 


GRASSLAND  CLIMAX. 


7 


base  association  of  Stipa-Bouteloua  into  a  pure  short-grass  cover.  Concrete  evidence 
of  this  has  been  obtained  in  widely  separated  areas  and  has  led  to  the  working  hypoth¬ 
esis  that  a  pure  short-grass  community  is  partly  if  not  largely  a  response  to  over- 
grazing.”  (Plant  Indicators,  115.) 

FURTHER  EVIDENCE. 

In  the  six  years  since  the  above  was  written,  a  large  amount  of  additional 
evidence  has  been  accumulated  as  to  the  unity  of  the  grassland  and  the 
close  phylogenetic  relationship  of  its  associations,  quite  apart  from  the  experi¬ 
mental  results  brought  forward  later.  In  fact,  the  detailed  field  study  of 
the  ranges  of  the  dominants  makes  it  clear  that  the  associations  are  even 
more  closely  related  than  was  at  first  supposed,  and  the  problem  becomes  one 
of  maintaining  several  of  these  units  as  distinct  rather  than  one  of  justifying 
their  inclusion  in  the  same  formation.  The  number  of  dominants  common  to 
contiguous  units  has  steadily  increased,  as  well  as  the  areas  concerned.  The 
most  unique  of  the  associations,  the  short-grass  plains,  has  been  shown  to  be 
a  recent  modification  of  mixed  prairie  due  to  overgrazing  and  has  been  more 
closely  connected  with  the  desert  plains.  The  widespread  dominants  that 
occur  in  all  the  climatic  associations  have  increased  in  number  and  now  com¬ 
prise  Stipa  comata,  Agropyrum  glaucum,  Bouteloua  gracilis,  B.  racemosa, 
Sporobolus  cryptandrus,  and  Koeleria  cristata. 

Even  more  striking  has  been  the  evidence  drawn  from  relicts  and  from  sea¬ 
sonal  variations  arising  out  of  the  climatic  cycle  (Clements,  1921,  1922,  1923). 
These  are  the  results  of  natural  experiments  on  a  scale  and  over  an  area  that 
can  not  even  be  approximated  by  the  experimenter,  and  their  value  is  of  the 
greatest,  especially  when  supplemented  by  control  experiments.  In  addition, 
the  repetition  and  checking  that  are  so  indispensable  are  not  only  provided 
by  recurrence  in  thousands  of  localities,  but  particularly  also  by  the  wide 
variation  in  behavior  from  season  to  season  at  the  wet  and  dry  phases  of  the 
climatic  cycle.  Of  the  first  and  the  most  direct  importance  are  the  relicts 
produced  by  overgrazing  and  by  rodents,  since  these  factors  have  operated 
directly  upon  the  normal  climax.  Such  relicts  permit  the  complete  recon¬ 
struction  of  the  original  community,  both  as  to  structure  and  extent.  Indeed, 
this  is  usually  done  in  the  most  graphic  fashion  by  nature  herself  during  sea¬ 
sons  or  phases  of  excessive  rainfall,  and  when  a  drought  period  of  several 
years  is  followed  immediately  by  a  year  of  exceptional  rainfall,  as  happened 
from  1916-1919,  a  revealing  picture  is  obtained.  The  expansion  and  con¬ 
traction  of  relict  areas  at  such  a  time  reproduces  in  miniature  what  occurs 
during  the  wet  and  dry  phase  of  a  major  climatic  shift  extending  over  a  period 
of  a  thousand  years  or  more.  In  the  light  of  grazing  relicts  and  cyclic  changes 
it  has  proved  possible  to  reconstruct  all  the  grassland  associations  in  detail 
as  they  were  before  the  historical  period  in  the  West.  Furthermore,  recon¬ 
struction  has  been  carried  much  farther  back  to  a  time  probably  10,000  to 
20,000  years  ago,  when  the  differentiation  of  the  grassland  mass  into  the 
various  associations  had  barely  begun.  In  short,  the  relict  method  confirms 
the  view  of  the  unity  of  the  grassland  climax  by  disclosing  several  stages  in 
the  differentiation  of  the  original  mass  and  affording  a  measure  of  the  extent  to 
which  this  has  progressed.  This  is  the  theme  of  the  volume  on  the  changes 
of  climate  and  grassland,  and  hence  it  will  not  be  further  elaborated  here. 


8 


INTRODUCTION. 


RELATIONSHIP  OF  THE  ASSOCIATIONS. 

The  above  suffices  to  indicate  what  appears  to  be  clearly  proven  by  the 
detailed  evidence,  namely,  that  the  relationship  of  the  six  communities  of 
the  grassland  is  a  phylogenetic  one.  This  seems  almost  obvious  in  the  case 
of  the  subclimax  prairie  and  the  short-grass  plains.  The  latter  is  demon¬ 
strably  a  grazing  subclimax  of  the  mixed  prairie,  though  such  a  hard-pan  area 
as  that  about  Burlington  may  be  an  actual  relict  of  a  short-grass  climax 
developed  during  the  last  major  dry  phase.  On  the  other  hand,  the  sub¬ 
climax  prairie  is  just  as  clearly  an  eastward  extension  of  the  taller  meadow- 
grasses  from  the  true  prairie,  made  in  response  to  the  same  climatic  shift 
and  profiting  by  fire,  especially  during  the  prehistoric  period.  These  changes 
are  still  so  recent  that  the  detailed  steps  can  be  readily  followed,  and  similar 
adjustments  can  be  traced  between  the  other  associstiona.  However,  the 
latter  have  been  largely  differentiated  at  an  earlier  period,  and  the  phylo¬ 
genetic  and  geographic  connections  are  less  broad. 

The  clue  to  the  relationships  of  the  four  actual  associations  is  to  be  found 
in  the  mixed  prairie,  which  most  nearly  represents  the  original  formation,  and 
consequently  affords  a  measure  of  the  divergence  of  the  others.  The  true 
prairie  stands  closest  to  the  mixed  prairie,  Agropyrum  glaucum  and  Koeleria 
cristata  being  common  dominants,  and  the  closely  related  Stipa  spartea  and 
S.  comata,  and  Sporobolus  asper  and  S.  cryptandrus  being  reciprocal  dominants 
in  the  two  respectively.  The  chief  difference  lies  in  the  fact  that  the  short- 
grasses  of  the  Stipa-Bouteloua  association  are  usually  absent,  or  form  a  frag¬ 
mentary  layer  in  the  true  prairie,  except  where  grazing  has  favored  their 
spread.  The  bunch-grass  association  resembles  the  true  prairie  in  the  absence 
of  the  short-grasses,  but  its  endemic  dominants  are  naturally  different,  e.  g., 
Agropyrum  spicatum,  Stipa  setigera,  and  Festuca  ovina  in  place  of  Stipa 
spartea  and  Sporobolus  asper.  Its  cognate  relation  to  the  mixed  prairie  is 
shown  by  such  common  dominants  as  Stipa  comata,  Agropyrum  glaucum,  and 
Koeleria  cristata,  and  by  the  persistence  to-day  at  the  higher  altitudes  in  the 
mixed  prairie  of  such  bunch-grasses  as  Stipa  setigera,  S.  eminens,  and  Festuca 
ovina.  The  desert  plains  bear  a  close  resemblance  to  the  short-grass  condition 
of  the  mixed  prairie,  the  reduction  of  the  upper  layer  of  tail-grasses  being  more 
a  matter  of  drought  than  of  grazing.  The  close  relationship  of  the  two  is 
shown  by  the  dominance  of  Bouteloua  in  both,  as  well  as  by  the  fact  that 
such  tail-grasses  as  Sporobolus  cryptandrus,  Bouteloua  racemosa,  Stipa  pen - 
nata,  and  S.  comata  persist  as  an  upper  layer  in  the  desert  plains  wherever 
protection  permits.  Moreover,  the  relict  areas  in  and  about  the  Mohave 
Desert  and  Death  Valley  prove  beyond  doubt  that  the  desert  plains  and  bunch- 
grass  associations  were  once  in  contact  and  that  at  an  antecedent  period  they 
were  commingled  and  probably  identical  (Clements,  1922,  1923). 

CLIMATIC  UNITY. 

The  fundamental  fact  in  the  relation  of  climaxes  to  climate  is  that  this 
must  be  determined  by  plant  judgments  rather  than  by  human  ones  (Plant 
Indicators,  116).  This  is  necessarily  truer  of  grasses  than  of  trees,  since  their 
life-habits  enable  them  to  minimize  or  escape  the  rigors  of  winter  as  well  as 
the  dangers  of  the  dry  season  of  the  year.  Consequently,  it  should  be  regarded 
as  neither  strange  nor  perplexing  to  find  such  great  grassland  dominants  as 
Bouteloua  gracilis,  Stipa  comata,  and  Koeleria  cristata  ranging  through  a  num- 


OBJECTIVES. 


9 


ber  of  climates  in  the  human  sense.  The  human  conception  of  a  climate  is 
loose  enough  at  best,  and  it  regularly  ascribes  much  greater  importance  to 
temperature  than  to  water  relations.  On  the  contrary,  grasses  are  more 
responsive  to  differences  of  rainfall  and  evaporation  than  to  those  of  tempera¬ 
ture,  Bouteloua  gracilis  in  particular  ranging  much  more  extensively  in  lati¬ 
tude  than  in  longitude  as  a  climatic  dominant.  This  is  confirmed  by  the 
construction  of  dominance  maps  of  the  chief  grasses,  which  disclose  the  fact 
that  the  interruption  or  disappearance  of  a  consociation  is  primarily  a  matter 
of  water,  a  conclusion  entirely  supported  by  the  present  investigation. 

In  addition,  it  must  be  recognized  that  obvious  differences  in  the  amount 
and  distribution  of  rainfall  may  have  slight  significance  for  grasses.  It  is 
the  amount  and  distribution  during  the  growth  period  of  the  grass  dominants 
that  controls,  and  this  is  equally  true  of  the  effect  of  evaporation.  The  mixed 
prairie  may  range  from  25  to  10  inches  without  undergoing  any  essential 
change  in  composition,  owing  to  the  fact  that  the  period  of  development  is 
shortened  to  fall  within  the  limits  of  optimum  water  conditions.  The  exist¬ 
ence  of  two  rainy  seasons,  as  in  southern  Arizona,  seems  to  indicate  an  impor¬ 
tant  difference  in  climate,  but  the  growth  of  the  grassland  is  still  an  effect  of 
the  much  more  adequate  summer  rains.  The  rainfall  of  the  Pacific  Coast  is 
of  the  winter  type  and  at  first  thought  appears  entirely  different.  However, 
this  is  only  apparently  true  in  so  far  as  the  native  bunch-grasses  are  con¬ 
cerned.  These  bear  the  same  general  relation  to  the  spring  rains  as  that  pre¬ 
vailing  in  the  mixed  prairie,  namely,  development  begins  during  the  rains, 
followed  by  maturity  and  the  drying  of  the  aerial  parts  in  late  spring  or  early 
summer  respectively.  The  differentiating  effect  of  the  peculiar  distribution 
of  rainfall  has  been  recorded  in  the  characteristic  life-form,  though  the 
progressive  assumption  of  the  bunch-grass  habit  is  revealed  by  the  fact  that 
it  is  found  in  practically  all  the  dominants  of  the  desert  plains  and  in  nearly 
all  the  tail-grasses  of  the  mixed  prairie. 

OBJECTIVES  OF  THE  PRESENT  INVESTIGATION. 

As  has  been  already  indicated,  the  primary  purpose  of  these  researches  is 
to  develop  an  experimental  method  that  will  combine  the  maximum  of  demon- 
strability  and  objectivity.  Because  of  its  size  and  apparent  complexity, 
vegetation  affords  an  open  field  for  prepossession  and  interpretation,  and  its 
study  can  be  made  scientific  in  the  proper  degree  only  by  the  resolute  employ¬ 
ment  of  experiment  and  measurement.  The  special  ends  of  this  investigation 
are  many,  chief  among  which  are  the  demonstration  of  the  unity  of  the  grass¬ 
land  climax  and  climate,  and  the  growing  differentiation  of  the  associations, 
partly  in  response  to  the  subclimates  and  partly  to  the  changes  wrought  directly 
or  indirectly  by  man.  It  has  also  proved  possible  to  cast  further  light  upon 
the  relationship  of  climatic  and  edaphic  areas  in  the  same  region,  as  well  as 
upon  the  significant  role  of  climatic  cycles  and  communi'y  shif tings  in  this.  A 
special  endeavor  has  been  made  to  analyze  competition  in  minuter  detail  and 
to  evaluate  more  fully  the  effect  of  light  intensity  in  a  grassland  cover.  Par¬ 
ticular  attention  has  been  directed  to  germination,  seasonal  ecesis,  and  final 
survival,  especially  in  relation  to  annual  variations  in  climate.  Finally,  the 
entire  study  has  been  designed  to  exemplify  a  new  aspect  of  the  phytometer 
method,  in  which  native  species  and  communities  have  received  the  major 
emphasis. 


10 


INTRODUCTION. 


STATIONS. 

Location. 

The  stations  were  chosen  to  represent  typical  conditions  in  each  of  the 
four  grassland  communities  occurring  in  the  vast  area  between  the  Missouri 
River  and  the  Rocky  Mountains.  Lincoln,  Nebraska,  was  selected  as  repre¬ 
sentative  of  true-prairie  conditions.  Aside  from  the  matter  of  convenience 
in  the  use  of  the  facilities  of  the  Department  of  Botany  of  the  University  of 
Nebraska,  the  vegetation  and  environment  of  this  region  are  better  known 
than  anywhere  else  in  the  grassland  formation,  due  especially  to  continued 
study  by  Pound  and  Clements  (1897,  1898,  1900),  Clements  (1905,  1907, 
1916,  1920),  Pool  (1914),  Weaver  (1917,  1919,  1920,  1921,  1922,  1923),  and 
others.  Phillipsburg,  in  north-central  Kansas,  was  selected  as  representative 
of  mixed-prairie  conditions,  while  Burlington,  in  eastern  Colorado,  was  chosen 
in  the  short-grass  plains.  Phillipsburg  lies  about  190  miles  southwest  of 
Lincoln,  and  Burlington  about  180  miles  further  west  and  south,  10  miles 


Fig.  1. — Map  showing  location  of  stations  in  the  four  grassland  communities. 

west  of  the  Kansas-Colorado  State  line  (fig.  1).  The  altitude  at  the  several 
stations  rises  from  1,100  feet  at  Lincoln  to  1,900  feet  at  Phillipsburg  and 
4,160  feet  at  Burlington.  Precipitation,  the  chief  factor  in  determining  the 
type  of  vegetation,  ranges  from  28  to  23  and  17  inches  at  the  respective  sta¬ 
tions,  decreasing  westward.  A  fourth  station  was  maintained  at  Nebraska 
City,  Nebraska,  about  50  miles  southeast  of  Lincoln,  near  the  Missouri  River. 
Although  the  rainfall  of  33  inches  is  sufficiently  ample  to  produce  scrubland 
or  woodland,  except  for  grazing,  mowing,  fires,  etc.,  this  station  lies  just 
within  the  border  of  the  subclimax  grassland  and  was  chosen  largely  because 
of  its  ready  accessibility. 

In  addition  to  the  four  stations  mentioned,  considerable  experimental  work 
was  carried  on  at  the  mixed-prairie  station  at  the  foot  of  Pike’s  Peak  near 
Colorado  Springs,  the  Alpine  Laboratory  being  used  as  a  base.  At  Lincoln 


STATIONS. 


11 


a  whole  series  of  stations,  ranging  through  gravel-knoll,  high  prairie,  low 
prairie,  salt-flat,  swamp,  and  cultivated  fields,  was  maintained.  Moreover, 
reciprocal  transplants  from  Tucson,  Arizona,  and  Berkeley,  California,  have 
been  made  at  many  of  the  stations. 

True-prairie  Stations. 

The  high-prairie  station  at  Lincoln  (plate  1)  was  located  on  a  rather  flat 
hilltop  about  60  feet  above  the  general  level  of  the  flood-plain  of  Salt  Creek 
and  2  miles  north  of  the  city.  The  fertile  soil  is  of  the  type  commonly  called 
loess,  but  is  really  a  glacial  drift.  It  is  a  silt-loam  belonging  to  the  Marshall 
series,  with  a  moisture  equivalent  of  about  28  per  cent  and  a  maximum  water 
capacity  of  approximately  60  per  cent.  The  mechanical  and  chemical  analyses 
of  soils  taken  from  an  adjacent  field  in  the  same  area  (Weaver,  1920:140) 
indicate  its  general  characteristics  (tables  1  and  2). 


Table  1 — Mechanical  analysis  of  high-prairie  soil. 


Depth  of  sample. 

Coarse 

gravel. 

Fine 

gravel. 

Coarse 

sand. 

Me¬ 

dium 

sand. 

Fine 

sand. 

Very 

fine 

sand. 

Silt. 

Clay. 

0.0  to  0.5  foot . 

p.  ct. 
0.0 

p.  ct. 
0.0 

p.  ct. 
2.0 

p.  ct. 
1.9 

p.  ct. 
6.0 

p.  ct. 

26  1 

p.  ct. 

39  3 

p.  ct. 

24  7 

0.5  to  1.0  foot . 

0.0 

0.0 

1.2 

2.2 

3.8 

21.8 

38.4 

32.6 

1  to  2  feet . 

0.0 

0.0 

2.7 

2.9 

4.8 

19  6 

45  6 

24  4 

2  to  3  feet . 

0.0 

0.0 

5.6 

6.9 

10.1 

23.1 

32.8 

21  5 

3  to  4  feet . 

0.0 

0.0 

7.0 

8.8 

12.8 

23.5 

28.3 

19.6 

Table  2. — Chemical  analysis  of  high-prairie  soil. 
[Digestion  with  HCL  (sp.  gr.  1.115)  for  120  hours.] 


Depth  of  sample. 

Insolu¬ 

ble 

resi¬ 

due. 

Solu¬ 

ble 

salts. 

Vola¬ 

tile 

mat¬ 

ter. 

Iron 
and  alu¬ 
minium 
oxid. 

Cal¬ 

cium 

oxid. 

Mag¬ 

nesium 

oxid. 

Phos¬ 

phorus 

pent- 

oxid. 

Nitro¬ 

gen. 

0.0  to  0.5  foot . 

0.5  to  1  foot . 

1  to  2  feet . 

2  to  3  feet . 

p.  ct. 

76.87 

75.70 

76.17 

77.80 

p.  ct. 

17.12 

18.58 

19.08 

18.46 

p.  ct. 
6.01 
5.72 
4.75 
3.68 

p.  ct. 

13.20 

14.25 

14.72 

14.03 

p.  ct. 
0.68 
.70 
.75 
.86 

p.  ct. 
1.19 
1.32 
1.68 
1.69 

p.  ct. 
0.13 
.12 
.12 
.15 

p.  ct. 
0.159 
.134 
.079 
.045 

The  soil  is  fine  in  texture,  being  composed  mostly  of  silt  and  clay,  and  is 
sufficiently  supplied  with  calcium  to  lack  acidity.  Determinations  through¬ 
out  a  number  of  years  show  that  the  subsoil  is  usually  moist  to  great  depths, 
although  at  infrequent  intervals  during  drought  periods  the  holard  may  be 
reduced  below  the  wilting-coefficient  of  Briggs  and  Shantz  (1912)  to  depths 
of  4  to  5  feet,  leaving  only  a  small  chresard  for  vegetation.  Root  excavations 
and  bisects  show  that  the  plants  are  not  only  rooted  deeply,  but  also  that 
the  root-systems  of  different  species  form  layers  in  the  soil,  the  shallowest  one 
ending  at  about  3  feet  and  an  intermediate  one  at  5  feet,  while  a  third  layer 
extends  far  below  this  level  (Weaver,  1920:28,  40). 


12 


INTRODUCTION. 


The  vegetation  is  distinctly  of  the  tail-grass  sod  type.  Andropogon  sco- 
parius,  Stipa  spartea,  Koeleria  cristata,  and  Bouteloua  racemosa  are  the  chief 
grasses,  although  Andropogon  f meatus  and  nutans  occur  more  or  less  along 
with  Poa  pratensis.  The  interstitial  Panicum  scribnerianum  and  the  relict 
Bouteloua  gracilis  are  of  much  less  importance.  Prevernal  societies  are  repre¬ 
sented  by  Antennaria  campestris  and  Carex  pennsylvanica.  Such  vernal 
bloomers  as  Astragalus  crassicarpus,  Baptisia  bracteata,  Senecio  plattensis,  and 
Nothocalais  cuspidata  are  abundant,  while  the  variety  and  abundance  of  esti¬ 
val  herbs  indicate  favorable  growth  conditions  throughout  the  early  summer. 
Chief  among  these  are  Psoralea  floribunda,  Erigeron  ramosus,  Brauneria  pal¬ 
lida,  Meriolix  serrulata,  and  Achillea  millefolium,  although  a  host  of  others 
occur  (Pound  and  Clements,  1900;  Weaver  and  Thiel,  1917).  Species  of 
Solidago,  Aster,  Liatris,  Helianthus,  Kuhnia,  etc.,  constitute  the  most  impor¬ 
tant  autumnal  societies,  the  subdominants  during  summer  and  autumn  giving 
a  truly  kaleidoscopic  appearance.  An  average  grass-level  of  6  to  8  inches 
and  an  upper  story  of  forbs  at  15  to  22  inches  is  attained  by  June  1,  although 
the  flowerstalks  of  Stipa  and  the  later  grasses  and  herbs  are  2.5  to  3.5  feet 
tall  (plate  1). 

Mixed-prairie  Station. 

This  occupies  an  area  just  south  of  Phillipsburg,  quite  typical  of  the  gently 
rolling  topography,  on  a  hillside  which  slopes  gently  southward  (plate  2a). 
The  fertile  soil  is  a  mellow,  dark-brown,  very  fine  sandy  loam  of  the  Colby 
series.  At  a  depth  of  12  to  15  inches  it  is  slightly  lighter  in  color  and  con¬ 
tains  enough  clay  to  be  quite  sticky,  although  when  wet  it  is  dark  in  color  to 
a  depth  of  2  feet.  Below  this  level  it  is  light  yellow  and  shows  its  loess  origin 
throughout.  The  first  4  feet  have  a  water-holding  capacity  of  about  66  per 
cent.  As  is  true  of  most  soils  of  semiarid  regions,  it  shows  no  acidity  at 
any  depth,  and  the  mellow  subsoil  is  very  deep. 


Table  3. — Mechanical  analysis  of  soil  at  Phillipsburg,  Kansas. 


Depth  of  sample. 

Coarse 

gravel. 

Fine 

gravel. 

Coarse 

sand. 

Me¬ 

dium 

sand. 

Fine 

sand. 

Very- 

fine 

sand. 

Silt. 

Clay. 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

0.0  to  0.5  foot . 

0.0 

0.0 

0.3 

0.2 

1.2 

43.5 

35.8 

19.0 

0.5  to  1  foot . 

0.0 

0.0 

0.0 

0.2 

0.5 

44.4 

32.8 

22.1 

1  to  2  feet . 

0.0 

0.0 

0.0 

0.2 

0.3 

39.7 

34.0 

25.8 

2  to  3  feet . 

0.0 

0.0 

0.0 

0.3 

0.6 

41.2 

31.9 

26.0 

3  to  4  feet . 

0.0 

0.0 

0.0 

0.1 

0.2 

37.5 

31.4 

30.8 

— 

Repeated  excavations  for  the  examination  of  the  roots  of  native  and  crop 
plants  from  1919  to  1921  showed  that  the  soil  was  moist  to  8  feet.  This 
condition  is  assumed  to  be  abnormal  for  the  region,  but  it  is  directly  to  be 
correlated  with  the  excessive  precipitation  of  1919  (Weaver,  Jean,  and  Crist, 
1922:77).  However,  this  station  is  somewhat  subject  to  drought,  the  holard 
to  a  depth  of  4  feet  being  sometimes  reduced  approximately  to  the  hygroscopic 
coefficient,  about  10.6  per  cent.  Under  these  conditions  the  native  vegetation 
is  rooted  almost  or  quite  as  deeply  as  in  the  true  prairie  (Weaver,  1920:93). 
The  vegetation  is  essentially  mixed  prairie,  the  tail-grasses  alternating  with 


STATIONS. 


13 


or  forming  a  layer  above  the  short  ones  (plate  2a).  Andropogon  scoparius, 
nutans ,  and  furcatus  often  form  more  or  less  continuous  irregular  sods  varying 
from  6  inches  to  7  feet  in  diameter,  from  which  short-grasses  may  be  almost 
entirely  excluded,  while  Agropyrum  glaucum  likewise  frequently  occupies  large 
areas  rather  exclusively.  Bouteloua  racemosa  and  Elymus  canadensis  are 
other  important  tail-grasses.  Alternating  with  these  are  similar  or  on  drier 
slopes  even  larger  areas  of  Bulbilis  dactyloides  and  Bouteloua  gracilis,  the 
intervals  being  nearly  devoid  of  vegetation,  often  to  the  extent  of  one-fourth 
of  the  surface.  More  usually,  however,  the  two  kinds  of  grasses  are  inti¬ 
mately  mixed,  the  short-grasses  often  showing  a  strong  tendency  toward  the 
bunch  habit.  Car  ex  filifolia  and  stenophylla  supplement  the  understory  of 
grasses,  the  leaves  of  which  reach  an  average  height  of  about  4  inches  (before 
flower-stalk  production),  as  contrasted  with  the  midsummer  tail-grass  level 
4  to  10  inches  above.  A  taller  open  layer  of  Psoralea  tenuiflora  at  2  feet 
characterizes  much  of  the  area  in  late  June,  when  societies  of  Ratibida  colum- 
naris  and  Morongia  uncinata  are  also  conspicuous.  However,  as  emphasized 
by  Clements  (1920:138),  the  mixed  prairie  shows  its  xerophytic  tendency 
by  less  numerous  and  less  extensive  societies.  Antennaria  campestris,  Astrag¬ 
alus  crassicarpus,  Nothocalais  cuspidata,  Anemone  caroliniana,  Senecio  plat- 
tensis ,  Vida  americana,  etc.,  are  all  represented,  even  if  sparingly,  in  the 
spring  and  early  summer,  but  the  absence  of  Viola,  Stipa,  Koeleria,  and 
Brauneria  is  at  once  noted,  and  the  presence  of  Astragalus  mollissimus,  Oxy- 
tropis  lamberti,  Malvastrum  cocdneum,  Opuntia  fragilis,  0.  camanchica,  Aristida 
purpurea,  and  Plantago  purshi  indicates  a  more  xerophytic  type  of  vegetation. 
The  sub  dominants  of  midsummer  are  usually  smaller  and  less  abundant  than 
eastward,  while  the  autumnal  aspect  likewise  lacks  many  species  common  to 
the  true  prairies.  The  part  of  the  mixed  prairie  used  for  experimental  planting 
was  carefully  selected  with  due  regard  to  a  proper  balance  between  tall  and 
short  grasses. 

Plains  Station. 

This  is  located  just  north  of  Burlington,  on  a  vast  level  tract  (plate  2b)  . 
The  soil  is  a  rich,  brown,  fine  sandy  loam,  very  compact  and  hard  when  dry. 
It  has  a  water-holding  capacity  of  65  to  70  per  cent  to  a  depth  of  4  feet.  At 
a  depth  of  2  to  2.5  feet  it  is  underlaid  with  a  so-called  hard-pan.  Soil  analyses 
show  that  the  concentration  of  colloidal  clay  and  carbonates  in  the  subsoil  is 
sufficient  to  give  rise  to  a  hard-pan,  i.  e.,  a  much  more  compact  intercalated 
stratum  of  soil,  upon  its  becoming  completely  dried  out  (Weaver  and  Crist, 
1922).  Silt  constitutes  about  one-third  of  the  soil  at  all  depths,  while  the  sand 
decreases  and  the  clay  increases  in  amount  to  4  feet  (table  4). 


Table  4. — Mechanical  analysis  of  soil  at  Burlington,  Colorado. 


Depth  of  sample. 

Coarse 

gravel. 

Fine 

gravel. 

Coarse 

sand. 

Me¬ 

dium 

sand. 

Fine 

sand. 

Very 

fine 

sand. 

Silt. 

Clay. 

Hygro¬ 
scopic  co¬ 
efficient. 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

0.0  to  0.5  foot. . 

0.0 

0.0 

0.0 

0.1 

2.6 

48.6 

33.4 

15.3 

10.9 

0.5  to  1.0  foot. . 

0.0 

0.0 

0.0 

0.1 

2.2 

49.1 

32.5 

16.1 

10.9 

1  to  2  feet . 

0.0 

0.0 

0.0 

0.2 

1.9 

46.7 

32.0 

19.3 

12.2 

2  to  3  feet . 

0.0 

0.0 

0.0 

0.1 

1.5 

45.5 

31.0 

21.9 

12.0 

3  to  4  feet . 

0.0 

0.0 

0.0 

0.1 

0.9 

42.2 

34.2 

22.6 

11.4 

14 


INTRODUCTION. 


Chemical  analyses  show  that  carbonates  are  practically  absent  in  the 
surface  soil,  but  increase  rapidly  with  depth,  and  often  reach  concentrations 
of  5  or  6  per  cent  in  the  hardpan  layer,  which  appears  somewhat  chalky  in 
color.  The  soil  is  not  at  all  acid;  the  carbon  dioxid  increases  very  rapidly 
with  depth  and  is  high  at  2  to  4  feet.  This  soil  is  rich  in  phosphorus 
and  potassium  and  has  a  sufficient  supply  of  nitrogen,  and  hence  all  the 
essential  raw  materials  are  present  in  abundance. 


Table  5. — Chemical  analysis1  of  soil  at  Burlington ,  Colorado. 


Depth  of 
sample. 

Acidity. 

Carbon 

dioxid. 

V  olatile 
matter. 

Phosphorus 

pentoxid. 

Sulphur 

trioxid. 

Potassium 

oxid. 

Nitro¬ 

gen. 

0.0  to  0.5  foot. . 
0.5  to  1.0  foot. . 

1  to  2  feet . 

2  to  3  feet . 

3  to  4  feet . 

p.  ct. 
None. 
None. 
None. 
None. 
None. 

p.  ct. 
0.03 
0.30 
1.71 
2.10 
2.60 

p.  ct. 
4.67 
3.13 
3.11 
3.34 
2.84 

p.  ct. 

0.189 

0.504 

0.428 

0.406 

0.525 

p.  ct. 
0.007 
0.017 
0.006 
0.006 
0.005 

p.  ct. 

2.32 

2.39 

2.45 

2.51 

2.22 

p.  ct. 
0.184 
0.130 
0.101 
0.086 
0.084 

1  Phosphorus  determinations  were  made  by  digestion  with  HN03  and  HF,  sulphur  by  fusion 
with  Na2C>2,  potassium  by  fusion  with  calcium  carbonate,  and  nitrogen  by  the  modified  Gun¬ 
ning  method. 


Water  penetrates  very  slowly  and  run-off  is  usually  high  in  this  fine- 
textured  soil.  Shantz  (1911)  has  shown  that  the  average  run-off  from  the 
short-grass  sod  at  five  stations  in  this  region  was  37  per  cent  of  the  total 
rainfall,  while  the  maximum  run-off  reached  55  per  cent.  Consequently,  the 
actual  precipitation  of  17  inches  is  a  poor  index  of  the  efficiency  of  the  rainfall. 
After  heavy  rains,  3  days  were  required  for  water  to  penetrate  to  a  depth 
greater  than  6  inches.  The  excellent  root  development  of  native  plants  in 
the  surface  1.5  to  2.5  feet  of  soil  enables  them  to  absorb  water  readily,  and 
further  prevents  a  deeper  penetration  of  rain.  Determinations  of  the  holard 
through  a  series  of  years  (1920  to  1923)  show  that  the  soil  is  seldom  moist 
below  2  feet,  while  by  midsummer  the  amount  above  this  level  is  frequently 
reduced  to  the  hygroscopic  coefficient.  When  this  happens,  the  short-grass 
cover  dries  out  and  “cures”  on  the  ground. 

Closed  mats  of  Bulbilis  dadyloides,  usually  mixed  with  Bouteloua  gracilis , 
make  up  fully  90  per  cent  of  the  vegetation,  forming  a  carpet  seldom  over 
inches  deep,  exclusive  of  the  flower-stalks  (plate  2b).  Agropyrum  glaucum  is 
frequently  associated  with  the  short-grasses,  but  overgrazing  and  drought 
have  resulted  in  a  dwarf  habit  and  it  forms  flower-stalks  sparingly,  except  in 
years  of  more  than  normal  rainfall.  These  grasses,  with  their  widely  spreading 
roots,  occupy  the  soil  so  thoroughly  that  relatively  few  important  sub¬ 
dominants  are  present.  Most  conspicuous  among  these,  and  increasing  in 
abundance  where  overgrazing  has  occurred,  are  Aristida  purpurea,  Opurdia 
camanchica,  O.fragilis,  0.  polyacantha,  Festuca  octoflora,  Plantago  purshi,  and 
Schedonnardus  paniculalus.  Erysimum  asperum  and  Psoralea  tenuiflora  also 
are  often  abundant,  while  small,  poorly  developed  societies  of  Astragalus 
crassicarpus,  Malvastrum  coccineum,  and  Ratibida  columnaris  are  infrequent. 
Decreased  size,  vigor,  and  number  are  characteristic  of  most  of  the  species 
when  compared  with  their  growth  in  more  favorable  conditions. 


CLIMATES. 


15 


While  some  of  the  species  of  the  meager  flora  are  rooted  entirely  in  the 
surface  soil,  others  reach  depths  of  4  feet  or  more,  especially  the  dominant 
grasses  and  the  legumes.  However,  even  these  are  relatively  shallow  when 
compared  with  the  great  depth  attained  by  species  in  the  moist  subsoil  of  the 
true  prairie. 

PHYSICAL  FACTORS. 

Rainfall  and  Holard. 

The  grassland  associations  concerned  lie  in  the  region  of  summer  rainfall; 
by  far  the  greater  part  of  the  rain  falls  during  the  growing-season  and  only 
about  one-tenth  during  the  three  winter  months  (fig.  2).  Such  a  seasonal 
distribution  of  the  precipitation  is  very  favorable  to  the  growth  of  grasses. 
The  normal  decrease  of  5  inches  at  Phillipsburg  in  comparison  with  Lincoln 
and  the  further  decrease  of  6  inches  at  Burlington  are  quite  evenly  dis¬ 
tributed  through  the  season.  Moreover,  the  type  of  rainfall  is  similar  through¬ 
out,  consisting  usually  of  heavy  showers,  often  of  rather  short  duration, 
though  this  is  more  marked  upon  the  high  plains  than  eastward,  where  che 
rains  are  more  general.  At  all  stations  it  results  in  much  run-off,  but  this  is 
particularly  heavy  on  the  compact  soil  at  Burlington.  However,  in  the  plains 
region  more  of  the  precipitation  falls  in  light  showers  of  0.2  inch  or  less,  which 
are  of  practically  no  value  in  increasing  the  holard.  At  each  station  the  holard 
has  in  general  been  very  similar  at  any  particular  time  during  the  three  seasons 
(1920  to  1922),  and  the  comparison  of  a  single  season’s  data  will  suffice  here 
(table  6). 


Fig.  2. — Mean  annual  precipitation  at  Lincoln  (solid  line),  Phillipsburg  (long 
broken  lines),  and  Burlington  (short  broken  lines). 

At  Lincoln  a  sufficient  amount  of  water  to  promote  good  growth  was  avail¬ 
able  at  all  depths  and  at  all  times.  At  the  mixed-prairie  station,  July  and  early 
August  were  periods  of  drought  and  at  times  of  actual  deficiency.  The  holard 
at  Burlington  was  favorable  until  June,  but  after  this  time  marked  defi¬ 
ciencies  were  of  frequent  occurrence.  However,  the  value  of  water-content  to 
the  plant  is  not  determined  entirely  by  its  quantity,  but  largely  also  by  the 


16 


INTRODUCTION 


Table  6. — Holard  in  excess  of  the  hygroscopic  coefficient  at  the  several 

stations,  1920. 


Lincoln,  Nebraska. 


Date. 

0  to  0.5 
foot. 

0.5  to  1 
foot. 

1  to  2 
feet. 

2  to  3 
feet. 

3  to  4 
feet. 

Apr.  10 . 

17.6 

16.1 

14.1 

10.0 

8.6 

Apr.  21 . 

17.5 

22.4 

20.3 

May  5 . 

20.5 

19.1 

19.7 

June  9 . 

18.7 

20.3 

June  16 . 

5.9 

12.5 

14.8 

15.6 

June  23 . 

4.9 

7.1 

9.6 

July  14 . 

22.0 

16.8 

9.1 

13.2 

14.7 

July  28 . 

7.2 

3.9 

6.3 

Aug.  5 . 

2.5 

4.0 

5.4 

9.7 

11.6 

Aug.  12 . 

8.7 

5.7 

4.8 

Aug.  19 . 

26.3 

7.7 

3.2 

Aug.  31 . 

Continued  heav1 

v  rains:  no  sanmles  taken. 

Wilting  coef . 

14.0 

12.9 

12.6 

10.5 

9.1 

Hygroscopic  coef . 

9.5 

8.7 

8.6 

7.1 

6.2 

Phillipsburg,  Kansas. 

Date. 

0  to  0.5 
foot. 

0.5  to  1 
foot. 

1  to  2 
feet. 

2  to  3 
feet. 

3  to  4 
feet. 

May  7 . 

14.7 

15.3 

12.5 

14.7 

14.0 

June  2 . 

4.8 

6.6 

11.6 

11.8 

13.0 

June  10 . 

7.6 

9.7 

9.0 

June  24 . 

6.6 

3.1 

5.0 

9.0 

July  1 . 

1.9 

4.1 

2.8 

July  9 . 

1.5 

2.8 

1.6 

July  21 . 

-1.4 

0.1 

-0.2 

2.3 

5.3 

Aug.  4 . 

0.7 

7.7 

-0.3 

0.5 

3.5 

Aug.  18 . 

12.6 

12.3 

5.4 

Aug.  26 . 

4.0 

4.1 

0.4 

2.0 

5.5 

Wilting  coef . 

13.3 

13.3 

13.4 

13.5 

13.1 

Hygroscopic  coef . 

10.6 

10.6 

10.9 

10.6 

10.7 

Burlington,  Colorado. 

Date. 

0  to  0.5 
foot. 

0.5  to  1 
foot. 

1  to  2 
feet. 

2  to  3 
feet. 

3  to  4 
feet. 

Apr.  15 . 

16.7 

13.7 

11 . 1 

4  9 

1  8 

June  3 . 

2.3 

5.2 

7.3 

6.9 

2  9 

June  12 . 

-1.8 

-0  1 

2  8 

June  25 . 

7.4 

2.5 

1  8 

1  4 

-2  5 

July  2 . 

-1.6 

-0.5 

0  0 

July  8 . 

-2.9 

-1.3 

-2.2 

July  20 . 

-0.7 

-2.7 

-1.7 

2.5 

-0.6 

Aug.  5 . 

4.6 

2.7 

-2.7 

-0.6 

-3  1 

Aug.  19 . 

-3.1 

-3.1 

-0.5 

Aug.  24 . 

-0.8 

-2.1 

-1  9 

-0.6 

14  5 

-1  4 

Wilting  coef . 

13.3 

13.3 

14  0 

14  0 

Hygroscopic  coef . 

10.9 

10.9 

12.2 

12.0 

11.4 

CLIMATES. 


17 


rate  of  loss  both  through  the  plant  and  by  surface  evaporation.  These  in 
turn  are  controlled  by  humidity  as  affected  by  temperature,  wind,  etc.,  all  of 
which  are  more  or  less  integrated  in  the  evaporation. 

June  July  August 


the  numbers  denote  the  first,  second,  third,  or  fourth  week  in  the  month, 
respectively. 


Fig.  4. — Average  day  (heavy  lines)  and  night  (fight  fines)  temperatures,  at  Lin¬ 
coln  (solid  fines),  Phillipsburg  (long  broken  fines),  and  Burlington  (short 
broken  fines),  1920. 


Temperature. 

Because  of  differences  in  elevation,  which  more  than  offset  those  of  latitude, 
spring  usually  opens  about  7  to  10  days  later  at  Phillipsburg,  and  18  to  23 


18 


INTRODUCTION. 


days  later  at  Burlington,  than  at  Lincoln.  These  stations  are  800  and  3,000 
feet  higher  respectively  than  Lincoln.  Air  temperature  was  usually  5°  to 
7°  less  at  Burlington  than  at  Phillipsburg,  and  also  lower  at  the  latter 
than  at  Lincoln.  Likewise,  the  average  day  temperatures  were  highest  at 
Lincoln  and  lowest  at  Burlington,  and  this  same  general  relation  held  for 
average  night  temperatures  (figs.  3  and  4).  The  night  temperatures  at 
Burlington  varied  from  45°  to  67°  F.  These  were  more  or  less  unfavorable 
to  growth,  but  their  chief  effect  was  probably  through  humidity,  differ¬ 
ences  of  temperatures  as  such  probably  having  little  effect  upon  the  type  of 
grassland. 


Fig.  5. — Average  daily  soil-temperatures  at  Lincoln  (solid  line),  Phillipsburg 
(long  broken  lines),  and  Burlington  (short  broken  lines),  1920. 


Soil  temperatures  were  highest  at  Lincoln  (70°  to  77°  F.)  and  lowest  at 
Burlington  (64°  to  72°  F.)  during  the  first  half  of  June,  but  by  the  last  week 
this  relation  was  reversed,  the  soil  at  Burlington  remaining  warmest  through¬ 
out  the  season  (fig.  5).  The  average  weekly  differences  were  often  as  great 
as  6°  to  8°  F.,  the  soil  at  Lincoln  being  coldest,  at  Phillipsburg  intermediate, 
and  the  dry  soils  at  Burlington  having  the  highest  temperatures. 

The  much  greater  daily  range  of  both  temperature  and  humidity  at  the 
Burlington  station  as  compared  with  that  at  Lincoln  is  shown  in  figure  6, 
and  the  average  day  and  night  humidities  for  1920  are  given  in  figure  7. 
Conditions  at  Phillipsburg  were  more  or  less  intermediate.  This  combination 
of  high  temperature  and  low  humidity,  which  occurs  rather  regularly  in  the 
afternoons  at  Burlington,  when  coupled  with  dry  soil,  obviously  promotes 
transpiration  and  depresses  growth. 


Wind  and  Evaporation. 

The  wind  movement  is  much  greater  at  Burlington  than  at  either  of  the 
other  stations  and  is  an  important  factor  in  desiccating  both  plants  and  soil. 
An  average  day  velocity  of  8  or  10  miles  per  hour  at  a  height  of  0.5  meter  is 
quite  usual,  while  periods  of  several  days  with  a  velocity  of  20  to  30  miles  per 
hour  are  not  uncommon.  The  amount  of  wind  is  less  at  Phillipsburg  and 
much  less  at  Lincoln  (for  example,  a  daily  average  of  4  miles  per  hour  from 


CLIMATES. 


19 


July  13  to  September  19,  1916).  The  evaporation,  which  in  a  measure  inte¬ 
grates  the  factors  of  radiant  energy,  humidity,  and  wind  movement  (fig.  8), 
was  greatest  throughout  the  season  of  1920  (23  to  60  c.  c.  average  daily 
evaporation  from  white  cylindrical  non-absorbing  atmometers)  at  Burlington, 


THURSDAY  FRIDAY.  SATURDAY.  SUNDAY. 


Fig.  6. — Hygrothermograph  records  from  Lincoln  (upper)  and  Burlington  (lower),  June  1921;  light 

lines  temperature,  heavy  lines  humidity. 

intermediate  at  Phillipsburg  (11  to  32  c.  c.),  and  least  at  Lincoln  (9  to  25 
c.  c.).  Similar  constant  differences  of  evaporation  rates  were  obtained  the 
following  seasons. 


20 


INTRODUCTION. 


In  consequence,  the  conditions  for  plant-growth  as  regards  rainfall,  holard, 
temperature,  humidity,  wind,  and  evaporation  are  normally  most  favorable 
at  Lincoln,  intermediate  at  Phillipsburg,  and  least  favorable  at  Burlington. 
These  conditions  are  indicated  by  the  native  vegetation  and  borne  out  by 
the  growth  of  crop  plants  (Weaver,  Jean,  and  Crist,  1922). 

June  July  August 


Fig.  7. — Average  day  (light  lines)  and  night  humidity  (heavy  lines)  at  Lincoln 
(solid  lines),  and  Burlington  (broken  lines),  1920. 


Fio.  8. — Average  daily  evaporation  at  Burlington  (short  broken  lines),  Phillips¬ 
burg  (long  broken  lines),  and  Lincoln  (solid  line),  1920. 


METHODS. 


21 


DETAILED  METHODS. 

Germination  of  Seed. 

In  these  experiments  the  fruits  and  seeds  of  a  large  variety  of  grasses’ 
forbs,1  shrubs,  and  trees  from  a  wide  range  of  habitats  were  employed. 
These  were  collected  in  quantity,  when  ripe,  chiefly  at  Lincoln,  Nebraska 
City  and  Halsey,  Nebraska;  Phillipsburg,  Kansas;  and  Burlington  and 
Colorado  Springs,  Colorado.  In  addition,  others  were  secured  from  the 
vicinity  of  Berkeley,  California;  Tucson,  Arizona,  and  in  lesser  quantities 
from  other  sources.  After  drying,  the  seeds  were  placed  in  large  cloth  bags 
and  kept  over  winter  in  a  dry,  well-ventilated,  unheated  building  at  Lincoln. 
A  new  crop  of  seeds  was  secured  each  season.  After  threshing  and  cleaning 
the  seed,  germination  tests  were  conducted  in  pots  and  flats  n  the  greenhouse 
of  the  University  of  Nebraska,  and  to  a  less  extent  in  moist  chambers  in  the 
laboratory.  This  was  primarily  for  the  purpose  of  eliminating  the  species 
that  germinated  rarely  or  not  at  all,  for  it  proved  possible  to  sow  seeds  even 
with  a  low  viability  so  thickly  as  to  secure  a  good  stand.  Seeds  from  plants 
growing  in  sand,  viz,  Calamovilfa  longifolia,  Muhlenbergia  pungens,  Redfieldia 
exuosa,  etc.,  were  germinated  in  sandy  soil. 

The  vitality  of  the  seeds  differed  greatly  from  season  to  season,  as  would  be 
expected.  Among  various  causes  for  this,  climatic  conditions  at  the  time  of 
anthesis  may  have  been  a  potent  factor.  In  some  cases,  early  frosts  on  low¬ 
lands  proved  harmful  to  the  unripe  seeds  of  late  species  of  grasses.  While 
the  1920  crop  of  Kuhnia  glutinosa  gave  no  germinable  seeds,  that  of  1921 
yielded  84  per  cent.  This  is  the  highest  record  for  any  species,  values  of  20 
to  25  per  cent  ( Psoralea  tenuiflora,  Ratibida  columnaris,  Stipa  viridula, 
Amorpha  canescens,  Desmodium  canescens,  and  Liatris  scariosa )  being  very 
good,  while  a  germination  of  10  to  15  per  cent  was  quite  usual.  Some  of  the 
legumes  germinated  very  slowly.  A  few  species  that  did  fairly  well  in  the 
greenhouse  {Amorpha  canescens  and  Aster  multiflorus)  gave  no  germination 
under  field  conditions  (1922). 

Depth  of  Planting. 

In  dealing  with  seeds  so  variable  in  size  and  natural  depth  of  planting 
(viz,  Sporobolus  asper,  Aster,  and  Solidago  as  compared  with  Stipa  spartea  and 
Gleditsia  triacanthus),  great  care  was  exercised  to  place  the  seed  at  such  a 
depth  as  to  favor  germination  and  establishment.  The  results  of  a  single 
greenhouse  experiment  upon  this  phase  of  the  problem  are  of  interest  (table  8). 
In  this  experiment  50  seeds  of  each  species  were  planted  at  various  depths  in 
loam  soil  of  good  tilth,  except  where  the  seeds,  because  of  small  size  or  low 
viability,  were  used  in  larger  but  equal  (measured)  numbers.  Sandhill  species 
were  grown  in  sandy  loam. 

These  results  show  that  depth  of  planting  has  a  pronounced  effect  upon 
germination  and  establishment.  This  is  due  in  most  cases  to  the  actual 
failure  of  the  seed  to  germinate  at  increased  depth  of  soil  and  in  others  to  its 
inability  to  grow  through  the  greater  thickness  of  soil  and  still  have  sufficient 

1  The  term  “forb”  is  here  used  for  herbs  other  than  grasses  in  order  to  afford  a  clear  cut  dis¬ 
tinction  and  at  the  same  time  avoid  an  awkward  phrase.  It  is  derived  from  the  Greek-Latin 

root  which  appears  in  4°pP4.  and  herba  (*ferb — ). 


22 


INTRODUCTION 


Table  7. — Germination  of  seeds.1 


Species. 

1919. 

1920. 

1921. 

1922. 

1923. 

Ar>pr  neonmdo^ . 

Fair . 

Fair . 

Acer  saccharinum . 

Fair . 

Seeds  fro- 

Good .... 

A  ornnvrnin  erlaiieiiTn  .  .  . 

zen;  no 
crop 

Poor . 

Good .... 

None. 

Arrmmlia  canescens . 

Good .... 

Andropogon  con  tortus5 . 

Poor . 

fnrnftt.ns  . 

Poor  .  _  . 

Poor . 

Poor . 

Poor. 

halli  . 

Poor . 

Poor . 

nnt.a.ns  . 

Poor  .... 

Good.  .  .  . 

Fair . 

Fair . 

Fair. 

ReonariiiR . 

Poor  .  .  . 

Fair . 

None.  .  .  . 

None .... 

Poor. 

Arcremono  nlatvceras1 * 3 . 

Poor . 

Ariatida.  rmrnnrpa1 . 

Good .... 

Poor . 

Excellent. 

Good .... 

Excellent . 

Aater  mnltiflorus . 

None .... 

Fair . 

None . 

.aalieifoliiiR . 

None .... 

None .... 

Astrn.palns  crassicarpus . 

None.  .  .  . 

Fair. 

Roiiteloiia.  bromoidea6 . 

Good .... 

erionoda,3 . 

None.  .  .  . 

gracilis . 

Good .... 

Excellent. 

Poor . 

Excellent . 

hiranta . 

Poor  .  .  . 

Excellent. 

Fair . 

Good .... 

None. 

racemosa . 

Fair . 

Poor . 

Excellent. 

Poor. 

racemosa5 . 

Good .... 

Fair . 

rnthroeki5  . 

None .... 

Rrannpria  pallida . 

None.  .  .  . 

Poor . 

None. 

Bulbilis  dactyloides . 

Fair. 

Calamovilfa  longifolia® . 

Fair . 

Very  poor 

Poor. 

GaRRia  chamaecrista . 

Fair. 

Cornus  canadensis2 . 

Very  poor 
Very  poor 

Gorylna  n.mericana2 . 

Desmodium  canescens . 

Excellent . 

Elymus  canadensis . 

Good.  .  .  . 

Excellent. 

Excellent . 

Excellent . 

Fraxinus  lanceolata2 . 

Poor . 

Fair . 

Fair . 

Gleditsia  triacanthus . 

Fair . 

Good .... 

Good .... 

Glycyrrhiza  lepidota . 

None.  .  . . 

None .... 

Helianthus  petiolaris3 . 

None.  .  . . 

rigidus . 

None .... 

None.  .  .  . 

None. 

Hilaria  rigida5 . 

None.  .  .  . 

Koeleria  cristata . 

Excellent. 

Excellent. 

Kuhnia  glutinosa . 

None .... 

Excellent. 

Excellent . 

Lespedeza  capitata . 

Poor . 

Fair . 

Fair . 

Fair. 

Liatris  punctata . .  . 

Excellent. 

Good .... 

Good .... 

Good. 

scariosa . 

Excellent 

Excellent. 

Good. 

Muhlenbergia  pungens6 . 

Fair . 

Fair . 

Onagra  biennis . 

Fair . 

Excellent . 

Excellent . 

Panicum  virgatum . 

Poor 

Fair . 

None.  .  .  . 

None .... 

Norte . 

Petalostemon  candidus . 

Fair . 

Excellent . 

Pdnus  ponderosa7 . 

Good.  .  .  . 

Good .... 

Good .... 

Psoralea  tenuifiora3 . 

None.  .  .  . 

Good .... 

Ratibida  columnaris3 . 

Good .... 

Redfieldia  flexuosa® . 

None .... 

Fair . 

Rhus  glabra . 

N one .... 

None .... 

Robinia  pseudacacia2 . 

Good.  .  .  . 

Good .... 

Salvia  pitcheri . 

None. 

Solidago  missouriensis . 

None .... 

Fair . 

serotina . 

None.  .  .  . 

None .... 

rigida . 

Fair. 

Sporobolus  cryptandrus3 . 

None .... 

Good .... 

asper . 

Excellent 

Good  .  .  , 

Excellent . 

Stipa  comata3 . 

Poor . 

Good .... 

Poor . 

Poor . 

spartea . 

None .... 

Poor . 

Poor  .... 

None. 

viridula3 . 

Good.  .  .  . 

None.  .  .  . 

Fair 

Excellent. 
None .... 

Good. 

Symphoricarpus  occidentalis . 

vulgaris . 

None . 

Ulmus  americana . 

Good. . . . 

No  crop, 
frozen 

Good .... 

1  All  seeds  were  collected  at  Lincoln,  unless  otherwise  indicated. 

1  Seed  from  Pennsylvania.  *  Seed  from  Arizona. 

1  Seed  from  Colorado  Springs.  «  Seed  from  sandhills,  Halsey,  Nebraska. 

4  Seed  from  Burlington.  1  Seed  from  Wyoming. 


METHODS. 


23 


reserve  material  to  establish  itself.  The  decrease  in  the  number  of  seedlings 
that  appeared  above  ground  was  due  in  part  to  this  cause,  but  especially  to 
damping-off  and  other  abnormal  conditions  arising  under  control.  With  the 
grasses  a  depth  of  planting  exceeding  0.5  to  1  inch  was  distinctly  detrimental, 
and  most  of  them,  like  the  composites,  did  best  at  0.12  to  0.25  inch.  Un¬ 
doubtedly,  aeration  and  frequency  and  amount  of  precipitation  exerted  a 
profound  effect  upon  ecesis  in  the  field.  Even  under  uniform  conditions, 
some  seeds,  e.  g.,  Elymus  canadensis ,  germinate  and  grow  rapidly,  while  others 
are  much  slower,  as  wrould  be  expected. 

Methods  of  Sowing  and  Planting. 

Seeds  and  fruits  of  plants  were  sown  under  three  different  sets  of  conditions 
at  the  several  field  stations,  namely,  surface-seeding,  trench,  and  denuded 
quadrat.  Surface-seeding  consisted  of  selecting  areas  with  a  typical  cover  of 
vegetation  in  which  wooden  stakes  bearing  the  names  of  the  species  were 
driven.  Near  the  stakes  and  without  disturbing  the  surface,  a  small  quantity 
of  seed  was  scattered.  A  little  debris  was  added  to  simulate  conditions 
during  fall  and  wdnter  after  the  seeds  have  fallen  naturally  from  the  plant. 


Table  8. — Germination  and  depth  of  planting. 


1 

Species  planted 
Mar.  24. 

Depth 

in 

inches. 

No.  of  plants. 

Apr. 

1. 

Apr. 

4. 

Apr. 

7. 

Apr. 

14. 

Apr. 

25. 

Remarks. 

Aristida  purpurea .... 

0.25 

8 

9 

5 

4 

3  lvs.  Apr.  25. 

0.5 

8 

23 

23 

23 

Same  size  as  those  at  0.25  inch 

1 

3 

8 

0 

0 

depth. 

2 

0 

0 

0 

0 

Agropyrum  glaucum1. 

0.5 

2 

16 

38 

49 

49 

4  to  5  in.  tall  with  3  lvs.,  Apr. 

1 

4 

18 

29 

25 

25 

40  • 

Same  size  as  preceding. 

2 

2 

4 

15 

14 

4 

All  smaller  than  preceding. 

3 

0 

0 

0 

0 

0 

Amorpha  canescens . . . 

0.25 

9 

11 

10 

8 

9 

1 

3 

7 

7 

5 

5 

Smaller  than  preceding. 

2 

0 

0 

0 

0 

0 

3 

0 

0 

0 

0 

0 

Andropogon  halli1 .... 

0.25 

5 

2 

4 

2 

3 

2  in.  tall,  3  lvs.,  Apr.  25. 

0.5 

0 

1 

1 

2 

2 

Same  as  above. 

1 

0 

3 

2 

2 

2 

Do. 

2 

0 

0 

1 

3 

3 

Nearly  as  large. 

Andropogon  nutans. . . 

0.25 

8 

7 

5 

2 

2 

Tillering. 

0.5 

0 

1 

1 

1 

1 

As  large  as  preceding. 

1 

0 

0 

0 

0 

0 

2 

0 

0 

0 

0 

0 

Bouteloua  racemosa1. . 

0.12 

14 

25 

27 

29 

3 

Progressively  smaller  to  the 

0.5 

20 

25 

17 

14 

0 

maximum  depth. 

1 

1 

25 

25 

32 

17 

2 

0 

8 

15 

8 

3 

Bouteloua  hirsuta1 .... 

0.25 

4 

10 

10 

10 

11 

3  or  4  leaves;  1.5  in.  tall. 

0.5 

4 

7 

9 

7 

7 

1 

1 

4 

4 

0 

0 

2 

0 

0 

2 

0 

0 

Desmodium  canescens. 

0.25 

2 

6 

16 

18 

18 

Largest,  with  5  leaves. 

1 

5 

11 

23 

24 

24 

Smaller  than  above. 

2 

0 

1 

11 

9 

9 

As  large  as  1  inch. 

3 

0 

0 

0 

0 

0 

'Number  of  seeds  not  counted. 


24 


INTRODUCTION 


Table  8. — Germination  and  depth  of  planting — Continued. 


Species 

planted 

Mar.  17. 

Depth 

in 

inches. 

No.  of  plants. 

1 

Mar. 

27. 

Mar. 

29. 

Apr. 

1. 

Apr. 

4. 

Apr. 

7. 

Apr. 

14. 

Apr. 

25. 

Remarks. 

Elymus  cana- 

0.12 

5 

8 

15 

14 

13 

13 

Poorest. 

densis.1 

0.5 

6 

16 

16 

16 

18 

18 

About  same  size. 

1 

0 

24 

24 

24 

29 

27 

2 

0 

13 

26 

28 

28 

22 

Smallest. 

Kuhnia  gluti- 

0  12 

Thick. 

Thick. 

Thick. 

Thick. 

Thick. 

Thick. 

nosa. 

0  5 

Thick. 

Thick. 

Thick. 

Thick. 

Thick. 

Thick. 

Smaller  than 

above. 

1 

A  few. 

Thick. 

Thick. 

Thick. 

Thick. 

Thick. 

Do. 

2 

0 

0 

0 

0 

0 

0 

Liatris  scariosa. 

0.25 

25 

27 

22 

18 

18 

16 

15 

4  to  5  in.  tall. 

1 

0 

0 

0 

0 

0 

0 

0 

2 

0 

0 

0 

0 

0 

0 

0 

3 

0 

0 

0 

0 

0 

0 

0 

Liatris  punc- 

0.25 

1 

12 

12 

13 

13 

12 

11 

2  to  3  in.  tall. 

tata. 

1 

0 

0 

0 

0 

0 

0 

0 

2 

0 

0 

0 

0 

0 

0 

0 

3 

0 

0 

0 

0 

0 

0 

0 

Muhlenbergia 

0.12 

20 

20 

12 

8 

8 

7 

2  tillers;  3.5  in. 

pungens.1 

tall. 

0.5 

20 

40 

50 

44 

35 

35 

1 

12 

16 

12 

12 

10 

10 

Smaller. 

2 

6 

14 

20 

20 

20 

20 

Smallest. 

Onagra  bien- 

0.12 

Very 

Very 

Very 

Very 

Very 

Very 

Very 

Excessive  com- 

nis.1 

thick. 

thick. 

thick. 

thick. 

thick. 

thick. 

thick. 

petition. 

0.5 

13 

20 

28 

35 

40 

Very 

Very 

Much  competi- 

thick. 

thick. 

tion. 

1 

3 

3 

3 

4 

4 

7 

7 

Largest  rosettes 

of  all. 

2 

0 

0 

0 

0 

0 

0 

1 

Very  small. 

Petalostemon 

0.25 

6 

6 

6 

6 

6 

7 

7 

2  in.  tall. 

candidus. 

0.5 

1 

1 

1 

1 

1 

1 

1 

0.5  in.  tall. 

1 

0 

2 

2 

2 

3 

3 

3 

Smaller,  very  del- 

icate. 

2 

0 

0 

0 

0 

0 

0 

0 

Ratibida  col- 

0.25 

2 

2 

3 

3 

3 

2 

3 

Rosettes  with  4 

umnaris. 

to  5  lvs. 

0.5 

2 

2 

3 

3 

3 

3 

4 

Smaller. 

1 

0 

0 

0 

0 

0 

0 

0 

Sporobolus  as- 

0.12 

8 

9 

28 

34 

35 

31 

31 

3  to  4  in.  4  lvs. 

per.1 

0.5 

5 

9 

20 

24 

22 

27 

27 

Large  as  above. 

1 

0 

4 

14 

34 

34 

5 

Pot  waterlogged. 

2 

0 

1 

2 

2 

4 

2 

1 

Smaller  than 

above. 

Stipa  viridula . . 

0.25 

25 

35 

39 

40 

38 

33 

33 

4  to  5  in.  3  lvs. 

1 

20 

22 

22 

24 

23 

23 

23 

Do. 

2 

0 

0 

3 

2 

4 

3 

2 

Much  smaller. 

3 

0 

0 

0 

0 

0 

0 

0 

1  Number  of  seeds  not  counted. 


This  was  sufficient  to  keep  the  seeds  from  being  blown  away.  Upon  germina¬ 
tion,  seeds  sown  under  such  conditions  meet  with  keen  competition  from  the 
established  vegetation  for  water  and  nutrients  below  ground  and  for  light 
above.  The  degree  to  which  light  intensity  is  reduced  under  the  grassland 
cover  has  never  been  adequately  emphasized,  but  frequently  it  is  as  low  as 
5  to  10  per  cent,  even  early  in  the  summer. 


METHODS. 


25 


The  trench  method  of  seeding  was  used  in  order  to  remove  competition 
both  below  and  above  ground  for  longer  or  shorter  periods.  Long,  narrow 
trenches,  approximately  4  inches  wide  and  deep,  were  cut  in  the  native  sod. 
The  soil  from  the  trench  was  then  thoroughly  pulverized  and  all  of  the  larger 
roots  and  rhizomes  carefully  removed,  after  which  it  was  again  replaced  in 
the  trench  Enough  additional  surface-soil  was  added  so  that  when  firmly 
compacted  the  level  of  the  trench  was  the  same  as  that  of  the  surrounding 
surface  This  detail  is  of  fundamental  importance,  since  the  amount  of  run-off 
or  the  amount  of  water  running  into  the  disturbed  area  is  thus  determined. 
Stakes  bearing  the  species  name  were  then  driven  in  place  at  about  12-inch 
intervals  and  the  seeds  planted,  the  soil  firmed,  and  a  little  loose  surface-soil 
added  as  a  mulch.  The  rapidity  with  which  rhizomes  and  neighboring  roots 
invade  this  newly  prepared  area  varies  considerably  with  the  type  of  vegeta¬ 
tion  and  climate,  as  also  the  rate  at  which  the  grasses  arch  over  the  trench 
and  reduce  the  light  intensity 

In  the  case  of  denuded  quadrats,  the  native  sod  was  removed  to  a  depth  of 
4  or  5  inches  over  an  area  about  2.5  feet  long  and  16  inches  wide.  The  soil  was 
pulverized,  the  plant  parts  removed,  and  the  surface  brought  to  such  a  height 
as  to  be  even  with  the  surrounding  sod  after  settling.  One  and  sometimes  two 
species  were  planted  in  each  quadrat  thus  prepared.  Rhizomes  of  Corylus 
americana  and  Symphoricarpus  vulgaris  and  occidentalis  were  transplanted  in 
1921.  Obviously,  root  and  rhizome  invasion  from  the  sides  would  affect  the 
area  in  the  quadrat  much  more  slowly  than  that  in  the  trench,  and  this  was 
also  true  of  shading.  Consequently,  the  quadrat  method  obviates  both  root 
and  especially  shoot  competition  for  a  considerable  period,  but  certain  other 
factors  more  or  less  unfavorable  to  growth  are  introduced. 

Since  the  most  critical  period  in  the  life  of  the  plant  is  that  of  ecesis,  the 
method  of  seedling  transplants  was  also  used.  Seeds  were  germinated  and  the 
seedlings  grown  in  an  unheated  greenhouse  in  loam  in  2.5  to  4  inch  flower¬ 
pots.  The  larger  pots  were  used  for  those  species  which  grew  most  vigorously 
and  whose  roots  penetrated  deepest.  Planting  was  timed  in  such  a  manner 
that  the  seedlings  were  well  established  and  3  or  4  weeks  old  before  trans¬ 
planting  them  into  the  grassland,  usually  early  in  May.  At  this  time  trenches 
were  prepared  in  the  way  already  described,  except  that  the  subsoil  in  the 
trench  was  well  watered  before  replacing  the  soil.  The  trench  was  half  filled 
with  soil,  and  the  seedlings  were  then  transplanted  without  injury  by  simply 
removing  the  entire  contents  of  the  pot  as  a  core,  placing  this  at  the  proper 
level  in  the  trench,  and  firming  the  soil  about  it.  A  sufficient  number  of 
plants  were  available  so  that  any  injured  in  removing  the  pot  were  discarded. 
After  watering  again,  the  trench  was  brought  to  the  proper  level  and  a  thin 
layer  of  loose  soil  applied.  If  the  weather  required  it,  the  trenches  were 
watered  for  a  10-day  period  during  establishment.  As  with  the  other  methods 
of  planting,  the  plants  were  thinned  from  time  to  time  to  reduce  competition 
when  necessary.  All  the  seedlings  were  grown  at  Lincoln  and  transported  to 
the  other  stations  as  needed. 

Finally,  a  fourth  method  was  used,  which  consisted  of  transplanting  mature 
plants  or  sods.  Blocks  of  sod  about  10  inches  square  were  selected  and  cut 
with  almost  vertical  sides  to  a  depth  of  8  or  10  inches  and  removed  with  the 
minimum  disturbance  of  the  underground  parts  above  the  level.  The  size 


26 


INTRODUCTION. 


varied  somewhat,  depending  upon  the  root-habit  and  nature  of  the  soil. 
In  transplanting  Bulbilis  dactyloides,  Bouteloua  gracilis ,  Muhlenbergia  gracil- 
lima,  and  other  species  with  fine,  dense  surface  roots,  the  blocks  were  often 
larger  but  not  so  deep.  Conversely,  transplants  from  sandy  or  gravelly  soil 
were  necessarily  smaller.  Many  forbs  were  also  transplanted,  care  being 
taken  to  wrap  each  block  securely  in  burlap  for  transportation.  By  this 
method  of  sod  transplants,  species  were  planted  reciprocally  among  the 
different  stations;  for  example  at  Lincoln,  Spartina  cynosuroides  was  trans¬ 
planted  from  swamp  to  salt-flat,  low  prairie,  high  prairie,  and  gravel-knoll, 
care  being  taken  to  replant  a  control  block  in  the  swamp  for  a  check.  In 
transferring  the  blocks  of  sod,  great  care  was  taken  to  make  a  hole  of  the 
exact  size,  so  that  the  transplant  was  in  good  contact  at  both  the  bottom  and 
sides,  just  enough  loose  soil  being  a*dded  and  firmly  tamped  around  the  block 
to  make  the  contact  complete.  The  sods  were  placed  2  or  3  feet  apart. 
Ordinarily,  root  and  rhizome  growth  had  more  or  less  obscured  the  lines  of 
disturbance  after  the  first  season,  unless  there  were  marked  differences  in 
soil  color  or  texture. 

As  far  as  possible,  transplants  were  made  preceding  or  coincident  with  the 
renewed  growth  and  at  a  time  when  the  holard  was  distinctly  favorable. 
Moreover,  green  parts  were  clipped  back,  often  level  with  the  soil,  in  order  to 
reduce  water-loss.  The  surplus  food  materials  of  the  older  roots,  rhizomes, 
etc.,  rendered  vigorous  growth  possible,  and  in  the  main  this  was  the  most 
successful  method  employed,  early-blooming  species  like  Koeleria  cristata  and 
Stipa  spartea  alone  sometimes  failing  to  seed  the  first  season.  The  others, 
such  as  Agropyrum  glaucum  and  Bulbilis  dactyloides,  not  only  fruited,  but  often 
also  extended  their  area  by  vigorous  propagation. 


2.  EXPERIMENTS  DURING  1920. 

HIGH  PRAIRIE,  LINCOLN. 

Surface  Sowing.  • 

Surface  sowings  of  6  species  were  made  on  the  high  prairie,  April  16.  The 
seed  was  obtained  at  Lincoln,  as  in  all  cases,  except  as  otherwise  stated, 
Stipa  viridula  from  Colorado  Springs  being  the  only  exception  in  this  instance. 
Koeleria  cristata  and  Stipa  alone  had  germinated  by  May  15,  and  Andropogon 
nutans  and  A.  scoparius  by  June  2,  while  the  seeds  of  Elymus  canadensis  and 
Aristida  purpurea  (seeds  from  Burlington)  did  not  germinate.  By  June  15, 
Stipa  and  A.  scoparius  were  mostly  dead  or  dying,  and  from  this  time  there 
was  a  steady  decline  until  August  30,  when  all  had  succumbed. 

It  is  interesting  to  note  that,  although  heavy  rains  occurred  immediately 
after  sowing  and  at  two  other  intervals,  only  two  species  had  germinated  by 
May  15.  Holard  determinations  show  no  indication  of  failing  moisture  in  the 
surface  6  inches  until  the  middle  of  June  (table  6),  but  this  is  no  criterion  of 
the  alternate  periods  of  wetting  and  drying  undergone  by  the  seeds  in  the 
surface  inch  of  soil.  The  drought  during  June  was  marked,  no  efficient 
precipitation  falling  from  the  7th  until  the  25th;  in  fact,  the  rainfall  was  less 


Fig.  9. — Monthly  precipitation  at  Lincoln,  1920-1922;  the  monthly  mean  is  shown 

by  heavy  cross-bars. 

than  half  of  the  normal  (fig.  9).  Drought  weakened  the  seedlings,  but  not  to 
such  an  extent  that  they  were  unable  to  survive  during  the  favorable  growing 
weather  of  July  and  August,  and  competition  for  light  undoubtedly  played  the 
decisive  role.  By  late  in  May  the  light  intensity  at  the  soil  surface  (where  the 


27 


28 


EXPERIMENTS  DURING  1920. 


prairie  was  burned  the  preceding  spring)  was  reduced  to  12.5  per  cent,  with  a 
range  of  2.5  to  26  per  cent  as  determined  by  the  stop-watch  photometer,  and 
later  in  the  season  this  was  much  further  decreased. 

Trench  Sowing. 

The  various  species  sown  by  this  method  all  germinated,  except  Koeleria. 
The  June  drought  resulted  in  the  loss  of  6  of  the  12  species,  nearly  all  of  which 
were  in  fine  condition  early  in  the  month.  Five  of  the  six  remaining  species 
not  only  survived  the  summer,  but  became  permanently  established.  The 
failure  of  the  four  introduced  species  is  of  interest,  especially  since  the  holard 
was  quite  favorable  for  growth  throughout  the  season  (table  6).  The  attenu¬ 
ated  condition  of  certain  species  noted  was  due  to  competition  for  light;  by 
midsummer  (July  25)  the  light  values  were  only  20  per  cent,  even  at  a  height 
of  4  inches  above  the  surface,  under  a  moderate  cover. 

Quadrat  Sowing. 

With  three  exceptions,  all  of  the  species  sown  on  the  surface  or  in  the 
trench  were  also  planted  in  denuded  quadrats.  Two  plantings  were  made,  one 
on  April  16  and  another  on  May  4  (table  58).  Although  the  June  drought 
made  its  impress  upon  the  seedlings,  all  but  three  species,  Koeleria  cristata 
Stipa  comata,  and  S.  coronata,  survived  the  summer.  In  fact,  the  following 
season  showed  that  all  of  these  were  permanently  established,  except  the 
California  stipas,  which  were  winterkilled.  It  is  interesting  to  note  that 
grasshoppers,  while  not  attacking  the  native  seedlings,  greedily  ate  the  intro¬ 
duced  ones  (except  Stipa  viridula).  This  alone  might  constitute  a  biological 
barrier.  Little  difference  was  noted  in  the  success  of  the  seedlings  planted 
at  different  dates.  At  both  plantings  the  soil  was  quite  moist  and  good  rains 
soon  followed.  Even  a  short  period  of  drought  after  germination  is  often 
disastrous,  as  can  be  understood  from  a  study  of  the  life-history  of  the  seed¬ 
lings.  Since  it  is  extremely  difficult  to  recover  with  certainty  the  delicate 


Fig.  10. — Plants  of  Bouteloua  gracilis  (A),  Bouteloua  hirsuta  (B), 
and  Sporobolus  asper  (C),  44-days  old;  scale  1  foot.  > 


HIGH  PRAIRIE. 


29 


roots  among  the  dense  tangle  of  the  native  sod,  plants  for  this  purpose  were 
grown  in  a  similar  soil  free  from  vegetation.  In  early  growth  these  were 
comparable  to  those  in  the  quadrats,  though  differences  occurred  later. 

Root  Habits  of  Seedlings. 

Plants  for  root  study  were  planted  in  fertile  cultivated  soil  on  April  20. 
The  roots  were  first  examined  on  June  3  and  4,  when  the  plants  were  about  44 


Fig.  11. — Bouteloua  gracilis  3  months  old. 
Fig.  12. — Bouteloua  hirsuta  3  months  old. 


days  old.  The  plants  of  Bouteloua  gracilis,  Sporobolus  asper,  and  Bouteloua 
hirsuta  were  3  or  4  inches  tall,  each  had  3  to  5  leaves,  and  most  of  them  were 
beginning  to  tiller  (figs.  10,  a,  b,  c).  The  position  of  the  seed  and  the  pro¬ 
nounced  branching  of  the  single  primary  root  are  clearly  evident,  and  the 
depth  of  7  to  11  inches  so  early  attained  is  significant.  Tillering  occurred 
simultaneously  with  the  development  of  a  secondary  root  system,  a  phenome¬ 
non  which  is  common  also  to  the  cultivated  cereals  (Weaver,  Kramer,  and 


30 


EXPERIMENTS  DURING  1920. 


Reed,  1923).  The  period  of  tillering,  before  the  new  roots  have  become  well 
established  in  the  moist  layers  of  soil,  is  a  very  critical  one  for  the  plant, 
drought  at  this  time  often  causing  great  mortality.  Where  a  little  erosion 
occurs,  it  may  be  plainly  seen  that  the  seedling  is  literally  hanging  on  to  life 
by  a  single  thread. 


By  July  11  to  14  the  root  development  of  Bouteloua  gracilis,  under  the  favor¬ 
able  growth  conditions  and  lack  of  competition,  had  a  height  of  foliage  of  about 
8  inches,  while  flower-stalks  12  to  18  inches  tall  bore  spikes  of  flowers  almost 
in  bloom.  However,  the  plants  in  the  quadrats  were  only  4  to  6  inches  tall. 
The  primary  root  was  still  plainly  distinguishable  from  the  abundant  widely 


MIXED  PRAIRIE. 


31 


spreading  or  deeply  penetrating  ones  of  the  secondary  system.  The  working- 
level  was  about  20  inches;  some  roots  reached  depths  of  33  inches  (fig.  11). 
Bouteloua  hirsuta  was  even  more  deeply  rooted  than  the  preceding,  although 
its  above-ground  parts  were  scarcely  so  well  developed  (fig.  12).  The  root 
penetration  of  Stipa  spartea  was  similar  to  that  of  the  gramas,  though  the 
two  or  three  roots  of  the  primary  system  alone  had  penetrated  deeply,  the 
larger  fleshy  branches  of  the  secondary  system  mostly  ending  at  a  depth  of 
about  8  inches.  The  plants  were  8  to  10  inches  tall;  the  parent  plants  had 
about  5  leaves  and  some  were  well  tillered  (fig.  13). 

The  development  of  Agropyrum  glaucum  is  shown  in  figure  14.  Aristida 
purpurea  at  this  time  had  formed  heavily  tillered  clumps  6  to  8  inches  tall, 
which  were  only  slightly  better  developed  than  those  in  the  prairie  quadrats. 
The  roots  had  a  working  depth  of  20  inches  and  a  maximum  penetration  of  32 
inches.  Plants  of  Elymus  with  a  height  of  12  to  15  inches  (compared  with  5 
inches  in  the  quadrats)  showed  a  similar  root  depth.  Stipa  viridula,  which 
also  grew  more  vigorously  in  these  plats,  with  a  height  of  8  to  10  inches,  had  a 
working  level  of  16  inches,  while  the  longer  roots  penetrated  33  inches  into  the 
moist  soil.  These  data  show  clearly  why  a  species,  after  the  hazards  of  the  first 
season  are  past,  has  much  greater  chances  of  survival. 

Summary  of  Planting  Results. 

With  respect  to  results  on  high  prairie,  the  germination  on  the  surface,  in 
the  trench  and  in  the  quadrats  was  66,  92,  and  100  per  cent  respectively,  and 
the  survival,  0,  45,  and  80  per  cent.  Most  of  the  introduced  species  were 
badly  damaged  by  grasshoppers,  although  some  in  the  quadrats  survived  the 
season  but  were  winterkilled.  Aside  from  these,  all  the  species  that  persisted 
to  the  end  of  the  first  season  became  permanently  established.  Andropogon 
scoparius,  A.  nutans ,  and  Bouteloua  gracilis  grew  well  in  both  trench  and 
quadrat. 

Sod  Transplants. 

Sods  of  the  following  species  were  planted  on  April  23,  mostly  in  triplicate. 
All  showed  some  drought  effects  during  June,  such  as  rolling  of  the  leaves,  but 
most  species  grew  normally  and  all  survived.  Among  those  from  the  high 
prairie,  Agropyrum  glaucum,  Elymus  canadensis,  Koeleria  cristata,  and  Stipa 
spartea  produced  seed,  while  Andropogon  scoparius  and  Bouteloua  racemosa 
failed  to  form  flower-stalks.  Bouteloua  gracilis  from  the  gravel-knoll  did  not 
blossom,  but  Distichlis  spicata  from  the  salt-flat  seeded  profusely.  Andro¬ 
pogon  nutans  was  the  only  species  from  the  low  prairie  which  did  not  fruit, 
A.  furcatus,  Poa  pratensis ,  Panicum  virgaium,  and  Spartina  cynosuroides  all 
producing  seed. 

MIXED  PRAIRIE,  PHILLIPSBURG. 

Surface  Sowing. 

Seeding  was  done  on  May  7  with  the  same  six  species  as  those  used  at 
Lincoln.  When  examined  on  June  10,  three  species  only  had  germinated, 
but  these  were  quite  abundant.  By  July  1,  two,  Koeleria  cristata  and  Stipa 
viridula,  had  died,  while  Elymus  was  represented  by  a  few  slender  narrow¬ 
leaved  plants  with  dead  tips,  which  succumbed  by  July  10.  Good  rains 


32 


EXPERIMENTS  DURING  1920. 


occurred  soon  after  planting  and  at  two  later  periods  in  May.  However,  an 
examination  of  the  rainfall  data  shows  that  the  precipitation  for  June  was  much 
less  than  half  of  the  normal,  as  at  Lincoln  (fig.  15).  No  rains  sufficient  even 
to  wet  the  surface-soil  fell  after  June  18  until  the  14th  of  July,  when  drought 
again  prevailed  until  late  July  (table  6).  The  attenuated  condition  of  the 
longer-lived  species  was  due  to  the  competition  for  light.  An  average  value 
of  28  per  cent  (range  2.8  to  80  per  cent)  was  determined  for  this  station  on 
June  11. 


Fig.  15. — Monthly  precipitation  at  Phillipsburg,  1920-1922;  the  monthly  mean  is 

shown  by  heavy  cross-bars. 


Fig.  16. — Monthly  precipitation  at  Burlington,  1920-1922;  the  monthly  mean  is 

shown  by  heavy  cross-bars. 


SHORT-GRASS  PLAINS. 


33 


Trench  and  Quadrat  Sowing. 

The  behavior  of  the  same  species,  sown  in  the  trench,  is  summarized  in 
table  9.  While  all  germinated,  two  died  by  July  1,  another  by  August  4,  and 
only  two,  Andropogon  scoparius  and  A.  nutans ,  grew  throughout  the  season 
and  became  permanently  established.  These  plants,  with  others,  did  much 
better  in  the  quadrats.  While  all  but  Arislida  germinated  by  July  1,  several 
showed  a  high  mortality  due  to  drought,  although  only  two  species  had  died. 
Conditions  became  drier  during  July  and  only  six  species  were  represented  by 
the  end  of  the  summer.  All  of  them  became  permanently  established,  Bou- 
teloua  gracilis  forming  flower-stalks  the  first  season. 

Thus,  there  was  a  mortality  of  100  per  cent  among  plants  where  the  seed 
was  surface-sown,  while  33  per  cent  survived  in  the  trench,  and  67  per  cent 
in  the  quadrats.  Andropogon  scoparius  and  A.  nutans  did  well  in  both  trench 
and  quadrats,  but  Bouteloua  gracilis  alone  flowered  the  first  year.  No  sods 
were  transplanted  at  this  station. 

SHORT-GRASS  PLAINS,  BURLINGTON. 

Surface  Sowing. 

The  account  of  the  growth  of  surface-planted  species  at  Burlington  is  brief. 
Of  the  13  species  sown  on  April  15,  evidences  of  germination  were  found  for 
only  6  on  June  11,  and  the  plants  of  two  of  these  species  were  dead.  By 
July  2,  three  species  alone  remained,  and  one  of  these,  Liatris  punctata,  died 
before  the  end  of  the  summer.  Bouteloua  gracilis  merged  into  and  became 
scarcely  distinguishable  from  the  native  sod;  Stipa  viridula  tillered  heavily 
and  was  over  6  inches  tall. 

Precipitation  records  show  that  showers  (0.25  to  0.63  inch)  fell  in  April  after 
seeding,  but  this  was  followed  by  no  efficient  rainfall  (0.15  inch  or  more) 
until  the  middle  of  May.  Another  drought  period  intervened  until  the  27th, 
when  0.25  inch  of  rain  fell,  after  which  drought  ensued  until  June  18,  all  of  this 
serving  to  emphasize  the  unfavorable  conditions  to  which  the  plants  were 
subjected  (fig.  16).  The  almost  constant  lack  of  rainfall  throughout  the 
summer  was  enhanced  by  the  frequent  high  winds,  low  humidity,  and  high 
evaporation  (figs.  7  and  8). 

Trench  and  Quadrat  Sowing. 

Thirteen  species  were  sown  in  the  trench  on  April  15.  Evidence  that 
Andropogon  nutans  and  Elymus  canadensis  had  germinated  was  found,  but 
both  species  had  died  and  none  germinated  later.  With  one  or  two  exceptions 
the  same  species  that  were  sown  on  the  surface  and  in  the  trench  were  also 
planted  in  denuded  quadrats.  Their  growth  throughout  the  season  is  shown 
in  table  60.  Seven  of  the  13  species  germinated;  all  but  four  were  dead  by 
July  2,  and  only  three  species,  Andropogon  nutans,  Stipa  viridula,  and  Liatris 
punctata,  became  established. 

A  summary  shows  that  33  per  cent  of  the  surface-sown  species  that  germi¬ 
nated  survived ;  all  of  those  in  the  trench  succumbed,  while  in  the  denuded 
quadrats  43  per  cent  lived  through  the  season  and  as  usual  became  established. 
Stipa  viridula  survived  both  on  the  surface  and  in  the  quadrats,  Bouteloua 
gracilis  on  the  surface,  and  Andropogon  nutans  and  Liatris  punctata  in  the 
quadrats. 


34 


EXPERIMENTS  DURING  1920. 


Sod  Transplants. 

Blocks  of  sod  of  the  following  species,  mostly  in  quadruplicate,  were  secured 
from  the  several  stations  at  Lincoln  and  planted  at  Burlington:  Agropyrum 
glaucum,  Andropogon  scoparius,  A.  furcatus,  Bouteloua  racemosa,  Elymus 
canadensis ,  Koeleria  cristata ,  Panicum  virgatum,  Poa  pratensis,  and  Stipa 
sparlea.  Before  planting  the  sods  in  the  holes  made  in  the  short-grass  mats, 
these  were  filled  with  water,  which  was  allowed  to  sink  into  the  deeper  layers 
before  the  block  was  tamped  in  place.  The  grasses  were  planted  in  two  long 
rows,  each  having  two  blocks  of  each  species,  and  several  feet  of  unbroken 
sod  thus  intervened  between  the  blocks.  After  planting,  all  were  thoroughly 
watered,  and  this  was  repeated  on  one  row  at  intervals  of  2  or  3  weeks  through¬ 
out  the  season,  as  proved  necessary.  It  was  found  later  that  the  watered 
row,  which  had  been  planted  only  2  or  3  feet  from  a  broken  area,  had  received 
some  run-off  water  from  the  furrow  separating  the  broken  field  from  the 
grassland. 

Although  none  of  the  transplants  died,  the  drought  affected  the  imwatered 
row  in  a  number  of  ways,  while  even  the  watered  plants  did  not  attain  normal 
development.  Nearly  all  of  the  former  exhibited  a  marked  rolling  of  the 
leaves  and  even  severe  wilting  at  times,  and  the  tips  on  several  species  as  well 
as  whole  plants  died  back  considerably.  Elymus,  Koeleria,  Panicum,  and 
Stipa  flowered  under  both  conditions,  but  the  flower-stalks  were  usually  fewer 
and  decidedly  shorter  in  the  un watered  row,  as  was  true  of  the  foliage  also. 
Thus,  the  maximum  leaf -height  of  Panicutn  under  the  two  conditions  was  13 
and  20  inches  respectively,  while  the  height  of  the  panicles  ranged  in  the  one 
case  from  7  to  13  and  in  the  other  from  19  to  20  inches.  Stipa,  Koeleria ,  and 
Elymus  seeded  in  both  habitats,  but  Agropyrum  and  Andropogon  furcatus  in 
neither,  while  A.  scoparius  and  Boutelaua  racemosa  each  had  a  single  flower- 
stalk  in  the  watered  area.  The  ultimate  fate  of  these  transplants  is  indicated 
on  pages  68-70. 

Summary  of  Experiments. 

The  results  of  the  1920  experiments  at  the  three  stations  are  summarized  in 
table  9. 


Table  9. — Summary  of  experimental  seeding,  1920. 


Method. 

Per  cent  of  germination.1 

Per  cent  of  germinated  species 
established. 

Lincoln. 

Phillips- 

burg. 

Burling¬ 

ton. 

Lincoln. 

Phillips- 

burg. 

Burling¬ 

ton. 

Surface-sowing . 

66 

50 

46 

0 

0 

33 

Trench . 

92 

100 

15 

45 

33 

0 

Denuded  quadrat  . . . . 

100 

90 

54 

80 

67 

43 

Average . 

86 

80 

38 

42 

33 

25 

1As  indicated  elswhere,  it  is  entirely  possible  that  some  seeds  germinated,  but  did  not  appear 
above  ground,  or  died  later  and  disappeared  between  visits  to  the  stations,  though  it  seems  prob¬ 
able  that  few  remnants  were  overlooked. 


Of  the  plants  surviving,  only  three,  Andropogon  nutans,  Bouteloua  gracilis, 
and  Stipa  viridula,  succeeded  under  at  least  one  condition  at  all  three  stations. 


CULTIVATED  AREAS. 


35 


.4  ndrcrpogon  scoparius  and  Bouteloua  hirsuta  grew  at  all  stations  but  Burlington, 
and  Liatris  punctata  at  all  but  Lincoln.  Elymus,  Bouteloua  racemosa ,  and 
Aristida  purpurea  lived  throughout  the  season  at  Lincoln  only.  In  most  cases 
a  somewhat  better  growth  occurred  at  Lincoln  than  westward.  For  example, 
Andropogon  nutans  was  7  to  10  inches  tall  at  Lincoln,  6  to  9  inches  at  Phillips- 
burg,  and  4  to  5  inches  at  Burlington  late  in  August.  Among  the  transplanted, 
about  70  per  cent  flowered  at  both  Lincoln  and  Burlington,  those  at  the  latter 
station  having  been  watered.  Of  the  unwatered  sods  at  Burlington,  53  per 
cent  had  flower-stalks,  but  some  had  only  one  each.  "While  the  transplants  at 
Lincoln  developed  quite  normally,  most  of  those  at  Burlington  were  much 
dwarfed,  even  when  watered. 

SEEDING  IN  CULTIVATED  AREAS  AT  ALL  STATIONS. 


True  Prairie. 


The  germination  and  growth  of  the  preceding  species  in  cultivated  soil  at 
the  several  stations  is  instructive.  In  every  case  a  good  seed-bed  was  prepared 
by  plowing,  disking,  harrowing,  etc.,  and  a  part  of  the  fields  used  in  growing 
experimental  crop-plants  (W eaver,  1920, 1922)  was  set  aside  for  native  vegeta¬ 
tion.  "Weeds  were  removed  from  time  to  time  by  hoeing.  In  these  experi¬ 
ments  the  trench  method  alone  was  used.  The  upland  station  at  Lincoln  was 
located  on  a  broad,  level  hilltop  of  silt  loam  adjoining  the  upland  prairie. 

.All  but  two  species,  Aristida  purpurea  and  Bouteloua 
hirsuta ,  germinated,  and  all  of  the  others  except 
Koeleria  came  through  the  first  season  successfully. 

Because  of  the  lack  of  the  root  competition  which  is 
regularly  encountered  by  plants  in  the  native  prairie, 
these  plants  suffered  less  from  midsummer  drought. 

The  tillering  was  much  heavier  and  the  plants  were 
in  all  respects  more  vigorous.  For  example,  Andro¬ 
pogon  nutans  was  7  to  10  inches  tall  in  the  prairie 
quadrats  and  12  to  17  inches  in  the  field  on  August 
30.  Elymus  was  4  to  8  inches  and  10  to  14  inches 
tall  and  Bouteloua  gracilis  4  and  9  inches  respectively 
in  the  two  habitats.  Like  Bouteloua  racemosa ,  both 
were  putting  forth  flower-stalks  in  the  cultivated  field. 

They  all  seeded  by  October,  together  with  Andropogon 
scoparius,  although  the  flower-stalks  of  A  ndropogon 
and  Elymus  were  dwarfed. 

Root  Development. 

The  striking  growth  made  by  these  native  species 
in  a  single  season  emphasizes  the  effect  of  the  removal 
of  competition,  as  shown  especially  by  the  root  devel¬ 
opment,  e.  g.,  Andropogon  scoparius,  with  a  maximum 
penetration  of  4  feet  (plate  3a).  Fully  mature  plants 
excavated  in  the  prairie  in  similar  soil  differed  mainly 
in  their  greater  depth  of  penetration,  about  5.5  feet 
("Weaver,  1919:4).  Siipa  viridula  (plate  3b)  had  a  well-developed  root  system, 
a  few  of  the  longer  roots  extending  to  the  33-inch  level,  but  compared  with  the 
roots  of  mature  plants  in  the  native  habit  at  the  root  system  had  scarcely 


Fig.  17. — Root  of  Liatris 
punctata  at  end  of  first 
season’s  gr  owth. 


36 


EXPERIMENTS  DURING  1920. 


begun.  At  Colorado  Springs  they  had  a  lateral  spread  of  over  1.5  feet  and 
a  working  level  of  nearly  11  feet.  The  roots  of  Elymus  canadensis  under¬ 
went  a  remarkable  development,  as  shown  in  plate  4a,  and  as  with  mature 
specimens,  most  of  the  roots  were  in  the  first  1.5  feet  of  soil.  However,  this 
year-old  plant  exceeded  in  depth  (34  inches)  any  excavated  in  grassland, 
and  especially  in  the  large  number  and  profuse  branching  of  its  roots. 
Liatris  punctata ,  though  only  3  inches  tall  and  with  but  2  leaves,  possessed 
a  tap-root  that  penetrated  to  a  depth  of  3.3  feet  (fig  17).  A  considerable 
supply  of  reserve  food  had  been  stored  in  the  enlarged  portion  of  the  tap, 
which  had  a  maximum  diameter  of  5  mm.  Mature  plants  reached  depths 
of  6  to  15  feet. 

Both  tops  and  roots  of  Bouteloua  racemosa  made  exceptional  growth;  one 
plant  was  photographed  and  excavated  on  August  25,  1919,  only  124  days 
after  the  seed  was  planted  in  the  greenhouse  on  April  23,  the  seedlings  having 
been  transplanted  to  the  field  on  May  10  (plate  4b).  Mature  plants  reach¬ 
ed  depths  of  5.5  feet.  Stipa  comata  and  Andropogon  nutans  attained  working- 
levels  of  18  and  28  inches  respectively  and  maximum  depths  of  34  and  48 
inches.  The  root  habit  and  extent  in  both  cases  were  similar  to  those  of 
mature  plants  (plate  4c). 

Mixed  Prairie  and  Short-grass  Plains. 

At  Phillipsburg,  six  species  were  planted  on  May  7  in  a  field  adjoining  the 
prairie  station.  Andropogon  nutans ,  A.  scoparius,  and  Koeleria  cristata  did 
not  germinate,  Aristida  purpurea  grew  until  midsummer  only,  while  Elymus 
canadensis  and  Stipa  viridula  both  prospered.  By  July  10  the  two  tillers  on 
each  plant  of  Elymus  were  practically  as  tall  as  the  parent,  but,  unlike  the 
plants  at  Lincoln,  none  produced  flower-stalks. 

At  Burlington  the  plantings  were  made  on  the  same  day  as  in  the  grassland, 
viz,  April  15.  The  following  either  did  not  germinate  or  died  soon  after 
germinating:  Andropogon  nutans,  A.  scoparius,  Aristida  purpurea,  Bouteloua 
gracilis,  B.  racemosa,  Koeleria  cristata,  Liatris  punctata,  Panicum  virgatum, 
Stipa  comata,  and  S.  setigera.  Stipa  viridula  made  excellent  growth  throughout 
the  summer,  reaching  a  height  of  8  to  12  inches.  A  thick  stand  of  Elymus 
canadensis  was  obtained,  but  the  plants  died  during  the  summer. 

To  summarize,  germination  of  83,  50,  and  18  per  cent  respectively  was 
obtained  at  the  several  stations  going  westward.  Among  those  which  germi¬ 
nated,  Koeleria  died  at  Lincoln  and  Aristida  at  Phillipsburg.  Elymus  was 
successful  at  these  two  stations,  but  flowered  only  at  Lincoln.  Stipa  viridula 
succeeded  at  all  three  stations,  doing  quite  as  well  or  even  better  westward. 
Seven  other  species  grew  at  Lincoln  but  not  elsewhere.  The  holard  of  the 
cultivated  fields  decreased  in  nearly  the  same  proportion  as  in  the  grassland 
at  the  several  stations.  The  response  of  the  seedlings  to  the  different  climates 
was  in  close  agreement  with  that  of  the  seedlings  and  transplants  in  the 
grassland. 

EXPERIMENTS  AT  OTHER  CLIMATIC  STATIONS. 

Subclimax  Prairie,  Nebraska  City. 

Character. 

The  subclimax-prairie  station  was  located  near  Nebraska  City,  on  a  gentle 
east  slope  somewhat  over  halfway  down  one  of  the  large  rolling  hills  char- 


SUBCLIMAX  PRAIRIE. 


37 


acteristic  of  the  topography  of  the  region.  It  was  situated  in  an  area  of 
native  grassland  of  over  125  acres  in  extent.  The  soil  is  a  dark-brown  fine  silt 
loam,  consisting  of  glacial  materials  intermixed  with  loess.  Below  1.5  feet  it  is 
quite  yellowish  in  color  and  shows  more  plainly  its  loess  origin.  The  high  per¬ 
centage  of  clay  and  silt  is  indicated  by  its  hygroscopic  coefficient,  which  is 
about  12  per  cent;  hence  it  is  very  retentive  of  moisture.  As  already  indi¬ 
cated,  the  precipitation  at  this  station  is  approximately  5  inches  greater  (33 
inches)  than  at  Lincoln.  This  additional  moisture  promotes  the  growth  of 
a  more  luxuriant  grassland  vegetation  and  permits  the  presence  of  a  large 
number  of  herbs  and  shrubs  found  rarely  or  at  least  much  less  abundantly 
in  true  prairie  (plate  7b). 

7 

6 


5 


4 


3 


2 


1 


0 


1 1 

1| 

ill 

4n 


Nov  Dec 


Fig.  18. — Monthly  precipitation  at  Nebraska  City,  1920-1922;  the  monthly  mean 

is  shown  by  heavy  cross-bars. 

As  shown  in  figure  18,  April  had  about  twice  the  normal  amount  of  precipita¬ 
tion.  Moreover,  this  was  well  distributed  and  probably  accounts  for  the 
high  percentage  (80)  of  germination.  However,  the  rainfall  of  May  was  far 
below  normal,  while  that  of  June  was  less  than  one-third  the  usual  amount, 
only  two  rains  falling  (0.35  inch  on  the  15th  and  0.70  on  the  25th).  July  was 
likewise  a  dry  month. 

The  dominant  grasses  are  Andropogon  nutans,  A.  Jurcaius,  A.  scoparius,  and 
Stipa  spartea.  Koeleria  cristata,  Poa  pratensis,  Bouteloua  racemosa,  Panicum 
virgatum,  and  Spartina  cynosuroides,  which  runs  far  up  the  ravines,  are  of 
lesser  importance.  The  regular  occurrence  of  A.  furcatus  and  Panicum  on 
highland  and  their  excellent  development  indicate  more  favorable  conditions 
for  growth  than  in  true  prairie.  The  seasonal  aspects  and  herbaceous  societies 
resemble  those  described  for  Lincoln  (Pound  and  Clements,  1900;  Thornber, 
1901).  Throughout  the  grassland,  even  on  the  ridges,  postclimax  com¬ 
munities  of  Ceanothus  ovatus ,  Amorpha  canescens,  and  Rosa  arkansana  occur, 
being  held  in  check  by  annual  mowing.  Symphoricarpus  vulgaris  and  occi- 


38 


EXPERIMENTS  DURING  1920. 


dentalis,  Corylus  americana,  Cornus  asperifolia,  Rhus  glabra ,  and  Xanthoyxlum 
americanum  invade  the  grassland  from  the  vantage-ground  of  fences,  hedge¬ 
rows,  and  ravines.  In  unmown  and  unpastured  areas  these  with  others, 
including  many  trees,  form  thickets  or  groves  overrun  with  Vitis,  Rubus, 
Ampelopsis,  Celastrus,  Smilax,  etc.,  indicating  the  approach  to  climax  condi¬ 
tions. 

Results. 

On  April  2,  ten  species  were  sown  on  the  surface  of  an  area  mown 
the  preceding  fall.  Aristida  purpurea  and  Bouteloua  gracilis  failed  to  germi¬ 
nate.  Stipa  viridida,  S.  comata  (like  Aristida ,  from  seed  collected  at  Colorado 
Springs),  Koeleria  cristata ,  and  Liatris  punctata  died  by  midsummer,  while 
A.  scoparius,  A.  nutans,  Bouteloua  hirsuta,  and  Elymus,  after  suffering  some¬ 
what  severe  mortality,  came  through  in  good  condition  and  became  perma¬ 
nently  established. 


Table  10. — Holard  in  excess  of  hygroscopic  coefficient, 
Nebraska  City,  1920. 


Date. 

0.0  to  0.5 
foot. 

0.5  to  1 
foot. 

1  to  2 
feet. 

2  to  3 
feet. 

3  to  4 
feet. 

Apr.  2 . 

24.2 

21.3 

18.3 

14.2 

12.6 

June  6 . 

14.2 

16.9 

17.9 

.... 

.... 

June  14 . 

16.7 

10.6 

.... 

.... 

.... 

June  21 . 

8.4 

6.7 

12.8 

.... 

.... 

June  30 . 

8.9 

7.9 

.... 

.... 

.... 

July  4 . 

9.8 

4.7 

7.1 

.  .  .  . 

.  .  .  . 

July  19 . 

4.5 

5.3 

7.3 

8.9 

9.9 

July  28 . 

2.3 

3.4 

4.9 

.  .  .  . 

.  .  .  . 

Aug.  4 . 

0.3 

1.2 

3.4 

6.1 

7.6 

Aug.  12 . 

9.7 

2.6 

3.1 

.... 

.  .  ,  . 

Aug.  19 . 

28.5 

3.9 

2.4 

.... 

.  .  .  . 

Aug.  28 . 

Hygroscopic 

12.4 

9.5 

5.2 

3.3 

5.5 

coefficient. 

12.1 

11.7* 

12.3 

13.7 

12.9 

The  attenuation  of  the  leaves  of  the  seedlings  became  noticeable  early  in 
June.  By  this  time  the  average  level  had  reached  11  inches,  above  which 
Stipa  (3  feet),  Euphorbia  corollata,  Silphium  integrifolium,  and  various  other 
herbs  occurred.  Light  values  ranged  from  2.5  to  40  per  cent. 

The  behavior  of  the  species  planted  in  the  trench  was  exceptionally  good. 
All  germinated  and  all  but  four  lived  through  the  season,  owing  to  the  rather 
favorable  chresard  of  early  summer,  which  promoted  rapid  root  growth 
(table  10). 

The  same  species  planted  in  the  quadrats  did  much  better.  All  germinated, 
became  established,  and  lived  throughout  the  summer.  As  usual,  a  fairly 
high  mortality  occurred  among  most  species  at  the  critical  period,  when  the 
primary  root  system  was  supplying  a  maximum  of  transpiring  area  before  the 
secondary  one  became  established.  As  a  consequence,  the  seedlings  thrived 
best  or  held  out  longest  about  the  edges  of  the  quadrats.  In  solving  this 
problem  a  comparison  of  conditions  within  the  disturbed  area,  as  compared 
with  that  in  the  undisturbed  grassland,  is  illuminating. 


r 


MIXED  PRAIRIE.  39 


Table  11. — Comparison  of  chresard  and  soil  temperatures  in  denuded  quadrats  and  in  adjacent 

undisturbed  grassland. 


Station. 

Date. 

Depth. 

Grass¬ 

land. 

Chresard. 

Denuded 

quadrat. 

Differ¬ 

ence. 

Remarks. 

inches. 

p.  ct. 

p.  ct. 

p.  ct. 

July  14 

0  to  6 

22.0 

14.0 

8.0 

Lincoln,  high  prairie. 

* 

..Do.  .  . 

6  to  12 

16.8 

12.1 

4.7 

June  14 

0  to  6 

6.8 

11.3 

-4.5 

r  Do... 

0  to  6 

10.7 

19.9 

-9.2 

Lincoln,  low  prairie. . 

.  .Do.  .  . 

6  to  12 

13.8 

20.2 

-6.4 

June  22 

0  to  3 

6.9 

-0.6 

•  •  •  • 

,•  Do.  .  . 

3  to  6 

•  •  .  . 

13.3 

•  ■  •  « 

June  21 

0  to  3 

2.0 

-4.2 

•  •  *  • 

Nebraska  City . 

< 

.  .  Do .  .  . 

3  to  4 

•  •  •  • 

17.9 

,  ,  .  , 

.  .Do.  .  . 

0  to  3 

•  •  •  • 

-2.6 

•  •  •  • 

Phillipsburg . 

J 

May  19 

0  to  3 

•  •  .  • 

5.8 

•  •  •  . 

.  .Do.  .  . 

0  to  6 

5.4 

12.9 

7.5 

Temperature. 

Station. 

Date. 

Depth. 

Remarks. 

Grass- 

Denuded 

Differ- 

land. 

quadrat. 

ence. 

inches. 

°C. 

°C. 

°C. 

Lincoln,  high  prairie. 

May  5 

Under  surface 

27.6 

16.2 

11.4 

1  p.  m.,  clear, 

hot. 

Lincoln,  low  prairie.  . 

.  . .  Do .  .  . 

.  .  .Do . 

22.5 

19.5 

3.0 

12  noon,  clear, 

hot. 

Lincoln,  gravel-knoll . 

June  14 

3 

26.5 

21.2 

5.3 

2  p.  m.,  clear, 

hot. 

Lincoln,  high  prairie. 

. .  .  Do .  .  . 

Under  surface 

37.0 

41.0 

4.0 

Do. 

Lincoln,  low  prairie.  . 

.  .  .  Do .  .  . 

1 

34.0 

47.0 

13.0 

2  p.  m.,  burned 

area. 

Do . 

.  .  .Do.  .  . 

3 

30.0 

38.0 

8.0 

Do. 

Lincoln,  gravel-knoll . 

.  .  .Do.  .  . 

1 

41.5 

46.0 

4.5 

2  p.  m.,  clear, 

hot. 

Do . 

.  .  .  Do .  .  . 

3 

37.5 

41.0 

3.5 

Do. 

Nebraska  City . 

June  21 

Under  surface 

58.0 

38.2 

19.8 

2h30m  p.  m., 

clear,  hot. 

Do . 

.  .  .Do.  .  . 

3 

37.6 

32.4 

5.2 

Do. 

It  is  evident  that  it  is  often  much  drier  in  the  quadrats,  the  soil  hotter,  and 
the  humidity  much  lower.  The  average  daily  evaporation  is  from  15  to  40 
per  cent  higher  in  the  bare  area.  These  conditions  are  obviously  unfavorable 
for  seedlings.  The  partial  shade  about  the  edges  of  the  quadrats  lowers  the 
temperature,  lessens  wind  movement,  increases  the  humidity,  and  undoubt¬ 
edly  accounts  for  the  seedlings  growing  here  when  drought  kills  them  else¬ 
where. 

Mixed  Prairie,  Colorado  Springs. 

Character. 

The  station  at  Colorado  Springs  was  located  on  a  hillside  sloping  gently 
southward  and  in  the  midst  of  a  great  expanse  of  mixed  prairie,  about  2  miles 


40 


EXPERIMENTS  DURING  1920. 


east  of  the  city.  As  typical  for  much  of  the  region,  the  soil  consists  of  a  light- 
colored  loam  intermixed  with  some  sand.  It  is  very  compact  and  run-off  is 
high;  at  a  depth  of  6  to  10  feet  it  is  underlaid  with  sand.  The  distribution  of 
the  rather  meager  precipitation  (15  inches)  throughout  the  year  is  very 
similar  to  that  for  other  stations.  The  holard  of  the  surface  foot  is  about  45 
per  cent  and  the  echard  8.2  per  cent.  Studies  of  the  water-content  throughout 
a  number  of  years  show  that  it  is  frequently  reduced  to  the  hygroscopic  co¬ 
efficient  in  the  surface  layers,  and  the  soil  may  become  very  dry  to  a  depth 
of  at  least  4  feet.  The  high  evaporation,  which  is  often  twice  as  great  as  in 
true  prairie,  accentuates  drought.  The  extremes  of  day  and  night  tem¬ 
perature  are  similar  to  those  at  Burlington.  The  high  day  temperatures 
cause  low  humidity  (frequently  5  to  15  per  cent)  in  the  afternoon  and  cor¬ 
responding  water-loss  from  both  plants  and  soil. 

The  climate  is  reflected  in  the  composition  of  the  grassland,  both  in  the 
absence  of  many  true-prairie  species  and  the  relative  dwarfing  of  the  others 
that  grow  in  this  habitat.  As  a  result  of  close  grazing  before  fencing  the 
station,  Bouteloua  gracilis  was  quite  dominant.  Other  shorfc-grasses  or  sedges 
were  Muhlenbergia  gracillima  and  Carex  pennsylvanica.  Stipa  comala ,  Andro- 
pogon  scoparius,  Agropyrum  glaucum,  Aristida  purpurea,  Koeleria  cristata, 
Bouteloua  racemosa,  and  Andropogon  furcatus  all  reappeared  after  cattle  were 
excluded,  the  latter  only  sparsely.  Artemisia  frigida,  Aragalus  lamberti,  Lupi- 
nus  argenteus,  Senecio  aureus,  Abronia  fragrans,  Chrysopsis  villosa,  Psoralea 
tenuiflora,  and  Argemone  platyceras  all  form  extensive  societies.  Ratibida 
columnaris,  Opuntia  camanchica,  0.  fragilis,  and  Thelesperma  trifidum  were 
somewhat  abundant.  Most  of  the  grasses  are  rooted  at  a  depth  of  3  to  5  feet, 
while  many  forbs  penetrate  much  more  deeply,  some  to  12  feet.  This  grass¬ 
land  never  reaches  the  luxuriance  of  true  prairie  and  consequently  light  played 
a  ver}^  minor  role  in  the  following  experiments. 

Results. 

The  seeds  of  9  species  were  planted  in  quadrats,  but  not  until  June  17. 
All  were  from  Lincoln  except  Aristida  purpurea  and  Stipa  viridula.  Bouteloua 
gracilis,  B.  hirsuta,  and  Koeleria  failed  to  germinate,  while  Liatris  punctata 
died  soon  after  germination.  Andropogon  scoparius,  A.  nutans,  Elymus 
canadensis,  and  Stipa  viridula  became  established,  but  like  the  others  were 
watered  from  time  to  time. 

On  June  9  the  following  sods  from  Lincoln  were  transplanted,  being  abun¬ 
dantly  watered  at  the  time  of  planting  and  at  several  intervals  afterward: 
Agropyrum  glaucum,  Andropogon  furcatus,  A.  scoparius,  Bouteloua  racemosa, 
Bulbilis  dactyloides,  Elymus  canadensis,  Koeleria  cristata,  Panicum  virgatum, 
and  Stipa  spartea.  Although  they  made  a  rather  poor  growth,  due  partly  to 
the  late  period  of  transplanting,  all  survived  the  first  season. 

EXPERIMENTS  AT  EDAPHIC  STATIONS. 

Gravel-Knoll  Station. 

Character. 

A  comprehensive  series  of  edaphic  stations  was  located  at  Lincoln,  all  within 
a  distance  of  a  half-mile,  ranging  from  gravel-knoll  through  high  prairie,  low 
prairie,  lowland  cultivated  field,  and  salt-flat  to  swamp. 


GRAVEL-KNOLL. 


41 


The  gravel-knoll  station,  which  was  only  300  feet  south  of  the  high  prairie, 
occupied  the  crest  of  a  steep  hill  about  60  feet  above  the  valley  of  Salt  Creek 
(plate  5a).  The  soil  is  a  drift  and  consists  of  very  porous  coarse  sandy  to 
gravelly  loam  with  a  water-holding  capacity  of  only  40  per  cent  of  its  dry 
weight.  At  a  variable  depth,  about  4  feet,  it  is  underlaid  with  clay.  The 
hygroscopic  coefficients  at  the  several  depths,  together  with  the  chresard 
during  1920,  are  given  in  table  12. 


Table  12. — Holard  in  excess  of  hygroscopic  coefficient. 


Date. 

0.0  to  0.5 
foot. 

0.5  to  1 
foot. 

1  to  2 
feet. 

2  to  3 
feet. 

3  to  4 
feet. 

Apr.  21 . 

13.3 

7.3 

13.3 

May  5 . 

14.2 

5.5 

15.1 

.  .  .  . 

.  .  .  . 

June  9 . 

4.6 

5.1 

.... 

.... 

.... 

June  16 . 

-0.2 

0.0 

4.1 

6.6 

.... 

June  23 . 

-1.1 

-0.2 

1.8 

.... 

.... 

July  15 . 

-0.9 

1.7 

2.6 

1.1 

5.8 

July  29 . 

-1.8 

-0.6 

8.1 

.  .  .  . 

.  .  .  . 

Aug.  5 . 

-1.9 

-1.7 

0.5 

1.4 

7.2 

Aug.  12 . 

3.3 

-1.3 

0.4 

.  .  ,  . 

.  .  .  . 

Aug.  19 . 

8.6 

2.3 

0.3 

.... 

.... 

Aug.  31 . 

Continued  heavy  rains;  no  samples  taken. 

Hygroscopic 

coefficient. 

5.2 

4.9 

3.1 

2.8 

7.4 

The  low  water-content  is  due  not  alone  to  the  nature  of  the  soil,  but  also  to 
the  steep  and  generally  south  slope,  which  produces  a  high  run-off  and  greatly 
increases  the  temperature.  These  factors,  together  with  greater  wind  move¬ 
ment  and  higher  evaporation  than  at  the  high-prairie  station,  subject  both 
soil  and  vegetation  to  frequent  drought.  The  area  was  dominated  by  rather 
open  mats  of  Bouteloua  gracilis  intermixed  with  B.  hirsuta,  which  Stipa 
spartea,  Andropogon,  and  other  tail-grasses  were  invading  with  difficulty  from 
their  foothold  in  the  silt  loam  farther  down  the  slope.  However,  the  transition 
from  one  soil  type  to  the  other  is  quite  abrupt  and  the  ecotone  correspondingly 
sharp,  a  narrow  belt  of  what  is  essentially  mixed-prairie  occupying  this  area. 

Behavior. 

Of  the  seven  native  species  sown  in  the  trench  on  April  16,  Aristida  purpurea 
and  Liatris  punctata  failed  to  germinate.  Elymus  canadensis  and  Koeleria 
cristata  were  all  dead  by  July  15,  together  with  Stipa  coronata  and  S.  setigera, 
dominants  introduced  from  California.  The  single  remaining  clump  of  Stipa 
viridula  was  disturbed  by  rodents  and  died  later,  leaving  only  Andropogon 
nutans  and  A.  scoparius  as  survivors  of  the  first  season.  Among  these  the 
mortality  was  very  high;  the  leaf-tips  of  many  plants  were  dead,  while  the 
best  plants  were  only  4  to  6  inches  tall.  In  the  quadrats  the  same  species 
did  even  more  poorly,  only  five  germinating.  One  of  these  died  by  June  2, 
while  all  of  the  others,  after  a  period  of  leaf-rolling,  wilting,  and  progressive 
drying  of  the  leaves,  succumbed  by  the  middle  of  July  or  not  long  afterwards. 

Sods  of  Agropyrum  glaucum,  Andropogon  scoparius ,  Bouteloua  racemosa , 
Elymus  canadensis ,  Koeleria  cristata,  and  Stipa  spartea  were  transplanted 
from  high  prairie  to  gravel-knoll  on  April  20.  Andropogon  furcatus,  A.  nutans, 
Boa  pratensis,  Panicum  virgatum,  and  Spartina  cynosuroides  were  also  trans- 


42 


EXPERIMENTS  DURING  1920. 


planted  here  from  the  low  prairie.  Duplicate  and  often  triplicate  blocks  of 
sod  were  used.  One  lot  of  each  was  watered  thoroughly  at  two  or  three  of  the 
most  critical  periods  during  the  summer.  On  June  15,  none  of  the  sods  having 
been  watered  since  transplanting,  Andropogon  furcatus  and  Panicum  were 
badly  wilted  and  the  leaves  on  Andropogon  were  rolled,  while  both  Koeleria 
and  Stipa  had  blossomed  earlier  than  elsewhere  and  the  plants  were  drying  at 
the  base.  Two  weeks  later,  no  rain  having  occurred  until  the  25th,  all  of  the 
unwatered  plants  had  either  ripened  seeds  and  were  drying  {Koeleria,  Poa, 
Stipa),  or  had  revived  as  a  result  of  the  rains,  but  were  again  in  a  wilted  state. 
During  August,  one  sod  of  Poa  and  another  of  Andropogon  scoparius  died, 
while  the  un watered  Agropyrum,  Andropogon  furcatus  and  another  A.  sco¬ 
parius  were  nearly  dead.  The  plants  with  a  rather  shallow  root  habit,  viz, 
Koeleria,  Stipa,  and  Elymus,  suffered  less,  probably  because  they  could  com¬ 
pete  more  successfully  with  the  gramas  for  water  in  the  surface  soil.  However, 
Bouteloua  racemosa  and  even  Spartina  survived  in  fair  condition,  although 
dwarfed.  In  addition  to  the  three  early  bloomers  already  mentioned,  Elymus 
and  Agropyrum  were  the  only  ones  that  flowered.  The  ultimate  fate  of  these 
species  is  indicated  later  (p.  83).  The  low  chresard,  or  its  entire  absence  during 
certain  periods  of  drought,  is  shown  in  table  12. 

Low-prairie  Station. 

Character. 

This  station  was  located  on  a  level  tract  at  the  foot  of  the  hill  about  60  feet 
below  the  high-prairie  and  gravel-knoll  stations  and  only  a  quarter  of  a  mile 
southward  (plate  5b).  The  soil  is  a  fertile,  dark-colored  silt  loam  of  the 
Wabash  series.  It  is  very  fine  in  texture,  being  composed  mostly  of  silt  and 
clay  (tables  13  and  14),  and  with  the  Truog  test  showed  no  trace  of  acidity. 
The  greater  amount  of  volatile  matter  and  the  greater  nitrogen-content  at  all 
depths  than  in  soil  from  the  upland  indicate  more  favorable  conditions  for 
plant  growth. 


Table  13. — Mechanical  analysis  of  soil  from  lowland  cultivated  area. 


Depth  of 
sample  (feet). 

Coarse 

gravel. 

Fine 

gravel. 

Coarse 

sand. 

Me¬ 

dium 

sand. 

Fine 

sand. 

Very 

fine 

sand. 

Silt. 

Clay. 

Moisture 

equivalent. 

0.0  to  0.5 .... 

0.1 

0.4 

2.2 

1.8 

5.0 

25.0 

41.3 

24.3 

27.7 

0.5  to  1.0  ft.  . 

0.3 

0.7 

2.1 

2.2 

5.0 

25.4 

38.8 

25.8 

27.9 

1  to  2 . 

0.2 

0.3 

1.3 

1.5 

3.7 

21.4 

40.8 

31.0 

30.6 

2  to  3 . 

0.0 

0.1 

0.4 

0.5 

1.7 

19.2 

43.4 

34.7 

32.9 

Table  14. — Chemical  analysis  of  soil  from  lowland  cultivated  area. 


Depth  of 
sample 
(feet). 

Insoluble 

residue. 

Soluble 

salts. 

Volatile 

matter. 

Iron  and 
aluminium 
oxids. 

Calcium 

oxid. 

Magne¬ 

sium 

oxid. 

Phospho¬ 
rus  pent- 
oxid. 

Nitrogen. 

0.0  to  0.5. . 

79.34 

12.96 

7.70 

9.57 

0.68 

0.75 

0.13 

0.218 

0.5  to  1 .  .  . 

79.63 

13.66 

6.71 

10.27 

0.63 

0.77 

0.10 

0.187 

1  to  2 . 

78.11 

15.83 

6.06 

12.11 

0.64 

1.01 

0.08 

0.135 

2  to  3 . 

74.78 

19.82 

5.40 

15.20 

0.76 

1.27 

0.09 

0.082 

LOW  PRAIRIE. 


43 


Moreover,  the  chresard  is  constantly  greater  than  on  the  high  prairie, 
though  the  area  is  well-drained  and  the  soil  is  never  waterlogged. 


Table  15. — Holard  in  excess  of  hygroscopic  coefficient. 


Date. 

0  to  0.5 
foot. 

0.5  to  1 
foot. 

1  to  2 
feet. 

2  to  3 
feet. 

3  to  4 
feet. 

Apr.  10 . 

28.7 

22.3 

21.8 

18.7 

18.8 

Apr.  21 . 

26.1 

•  •  •  • 

22.1 

•  •  •  • 

•  •  •  • 

May  5 . 

33.1 

25.6 

23.9 

•  •  •  • 

a  a  •  • 

June  9 . 

25.7 

24.0 

•  •  •  • 

•  •  •  • 

June  16 . 

13.6 

16.6 

19.5 

26.4 

June  23 . 

9.3 

11.5 

20.4 

•  •  •  • 

July  14 . 

27.4 

21.1 

17.0 

19.5 

22.7 

July  28 . 

17.6 

12.5 

15.7 

•  •  •  • 

a  a  a  a 

Aug.  5 . 

2.3 

8.2 

11.5 

12.0 

23.6 

Aug.  12 . 

15.4 

12.4 

11.8 

•  •  •  • 

a  a  a  a 

Aug.  19 . 

21.8 

8.8 

10.1 

a  •  •  ■ 

a  a  a  a 

Aug.  31 . 

Continued  heavy  rains;  no  samples  taken. 

Hygroscopic 

coefficient. 

11.8 

11.1 

10.3 

10.2 

11.9 

The  low-prairie  area  is  dominated  by  a  few  species  less  xerophytic  than 
those  occurring  on  the  high  prairie.  Many  of  the  species  of  the  high  prairie 
are  absent,  but  are  replaced  in  part  by  others  of  a  more  mesophytic  kind. 
The  dominant  grasses  are  Andropogon  furcatus,  Panicum  virgatum,  Andropogon 
nutans ,  and  Spartina  cynosuroides,  each  of  which  often  covers  small  areas 
with  a  pure  or  nearly  pure  growth.  Poa  pratensis  is  also  very  important,  but  is 
overtopped  by  the  taller  grasses,  which  reach  a  height  of  5  or  6  feet  (plate  6a). 
Characteristic  forbs  are  Solidago  canadensis ,  S.  rigida,  Glycyrrhiza  lepidota, 
Aster  multiflorus,  A.  salicifolius,  Phy satis  heterophylla,  Polygonum  muhlenbergi, 
Artemisia  gnaphalodes,  Achillea  millefolium,  and  Callirrhoe  alcaeoides.  The  rank 
growth  forms  a  dense  cover  and  makes  ecesis  in  the  area  very  difficult.  Bisects 
show  that  the  plants  are  rooted  deeply,  most  of  them  reaching  depths  of  5 
to  12  feet.  Root-layers  at  3  and  5  feet  are  quite  as  distinct  as  those  on  the 
high  prairie. 

Behavior. 

Surface  sowings  of  eight  species  were  made  on  April  10.  Two  failed  to 
germinate,  while  Bouteloua  gracilis  germinated  but  soon  died.  By  June  15 
all  were  very  delicate  and  much  attenuated,  owing  to  the  low  light  intensity. 
A  month  later  Liatris  punctata  had  been  shaded  out  and  the  others  were 
slender  and  pale  in  color.  Stipa  viridula  and  Andropogon  scoparius  died 
later,  leaving  attenuated  individuals  of  A.  nutans  and  Koeleria  surviving 
the  first  season.  Koeleria  had  disappeared  by  the  following  spring,  but  A. 
nutans  made  a  good  growth  and  merged  into  the  native  sod.  The  light 
intensity  under  the  cover  of  tail-grasses  was  so  reduced  as  to  constitute  the 
major  factor  in  competition,  in  view  of  the  high  holard.  On  June  14,  1922, 
in  a  portion  of  the  prairie  burned  over  the  preceding  spring,  the  light  intensity 
under  vegetation  of  average  density  and  with  an  average  height  of  12  inches, 
was  only  6  per  cent.  Some  seedlings  were  growing  in  even  deeper  shade.  By 
July  25  the  average  had  dropped  to  3.5  per  cent;  under  a  thin  cover  it  was 
12  per  cent,  but  where  the  vegetation  was  very  dense,  only  1.5. 


44 


EXPERIMENTS  DURING  1920. 


Seeds  planted  in  the  trench  at  the  same  time  did  somewhat  better. 
Although  three  species  failed  of  germination,  all  of  the  others,  viz,  Andropogon 
nutans ,  Bouteloua  hirsuta ,  Elymus  canadensis ,  and  Stipa  viridula,  came 
through  the  season,  although  somewhat  blanched  and  attenuated.  Thus,  A. 
nutans  had  reached  a  height  of  7  to  8  inches  as  compared  with  a  growth  of  5  or 
6  inches  on  the  high  prairie.  Light  in  the  trench  in  June  varied  from  5  to  10 
per  cent  near  the  edge  to  50  or  60  per  cent  in  the  center.  By  late  July  this 
was  reduced  to  4.5  to  16  per  cent,  even  at  4  inches  above  the  surface.  Of  the 
eleven  species  sown  in  denuded  quadrats,  all  germinated,  and  all  but  one, 
Stipa  coronata ,  came  through  the  season  in  excellent  condition.  In  fact, 
except  for  Stipa  setigera,  which  was  winterkilled,  all  became  established. 
The  marked  development  shows  the  possibilities  of  growth  in  this  habitat 
when  sufficient  light  is  available.  Little  difference  was  apparent  between 
the  earlier  and  later  sowings. 

A  comparison  of  growth  in  the  denuded  quadrats  of  the  prairie  and  in  the 
adjoining  cultivated  area  is  of  interest.  Both  were  seeded  on  the  same  dates, 
weeds  being  kept  out  of  both  areas.  The  native  vegetation  in  the  field  was 
consequently  free  from  any  competition.  Aristida  purpurea,  Stipa  comata, 
S.  eminens,  and  S.  setigera  failed  to  germinate,  as  did  also  the  sowing  of 
Andropogon  nutans,  A.  scoparius,  and  Koeleria  cristata  made  on  April  9.  All 
others  made  an  excellent  growth,  even  exceeding  that  in  the  quadrats.  For 
example,  the  height  in  inches  attained  by  August  30  by  typical  representatives 
in  field  and  grassland  respectively  were :  Stipa  viridula,  20  and  5  to  7 ;  Koeleria 
cristata,  3  to  4  and  2  to  3;  Elymus  canadensis,  14  to  16  and  7  to  11.  Moreover, 
the  species  in  the  cultivated  area  were  more  heavily  tillered  and  three, 
Andropogon  nutans,  A.  scoparius,  and  Elymus,  came  into  blossom  in  Sep¬ 
tember.  The  root  systems  were  well  developed;  the  roots  of  Elymus  reached 
a  maximum  depth  of  4  feet  and  those  of  Andropogon  scoparius  were  abundant 
to  3  feet,  while  some  extended  to  4.5  feet.  The  roots  appeared  finer  than  on 
older  plants  and  were  not  so  well-branched  near  the  tips.  The  ample  water- 
content  of  the  fertile  soil  in  the  cultivated  area,  which  was  similar  to  that  on 
low  prairie,  together  with  the  lack  of  competition,  accounts  for  the  excellent 
growth. 

Blocks  of  sods  of  the  same  species  used  on  the  gravel-knoll  (except  Andro¬ 
pogon  nutans)  and  secured  from  the  same  sources  were  transplanted  into  low 
prairie  from  March  22  to  April  24.  Bulbilis  dactyloides  from  overgrazed  low 
prairie,  Distichlis  from  salt-flat,  and  Bouteloua  gracilis  from  gravel-knoll  were 
also  included.  The  prairie  had  been  mown  the  preceding  year.  During  the 
first  season  all  of  the  plants  flourished,  including  the  short-grasses,  Bulbilis 
and  Bouteloua  gracilis.  The  former  produced  stolons  abundantly,  but  none 
were  able  to  become  rooted.  Because  of  light  conditions,  the  height  growth 
of  the  shorter  grasses  was  somewhat  emphasized,  while  that  of  the  taller 
species  was  quite  normal  for  lowland.  All  the  transplants  flowered  the  first 
season,  except  Spartina.  The  effect  of  a  reserve  food-supply  in  the  roots  and 
rhizomes  is  shown  by  comparing  a  single  season’s  growth  of  Andropogon  nutans 
from  a  block  of  sod  in  the  low  prairie  and  from  seed  sown  in  the  lower  culti¬ 
vated  plats  (plate  8a). 

Salt-flat  Station. 

Character. 

This  station  is  located  on  a  level  tract  of  land  just  below  and  only  200  feet 
south  of  the  low  prairie.  Owing  to  a  small  percentage  of  sodium  chloride  which 


SALT-FLAT  AND  SWAMP. 


45 


has  deflocculated  the  clay  (table  16),  it  is  of  a  very  different  consistency 
from  that  of  the  low  prairie  (Hall,  1920:  283).  Moreover,  the  adsorption 
of  the  Na  ion  in  part  has  left  the  soil  in  a  slightly  acid  condition,  according  to 
Truog's  test. 


Table  16. — Acidity  and  salt-content  at  salt-flat  station. 


Depth  of 
sample. 

Acidity.1 

Total  soluble 
salts.2 

Chlorides. 

p.  ct. 

p.  p.  m. 

p.  ct. 

p.  p.  m. 

0.0  to  0.5  foot. 

Slight . 

0.17 

1,700 

0.06 

600 

0.5  to  1.0  foot . 

Very  slight  . 

1.14 

11,400 

.18 

1,800 

1  to  2  feet .... 

...  Do . 

.46 

4,600 

.10 

1,000 

2  to  3  feet .... 

.  .  .Do . 

.50 

5*000 

.12 

1*200 

3  to  4  feet .... 

. .  .Do . 

.64 

6,400 

.15 

1,500 

1  Neutral  to  litmus  in  water-extract.  2  No  carbonates  were  present. 

The  above  conditions,  as  the  holard  is  very  similar  to  that  in  the  low 
prairie,  have  greatly  affected  the  type  of  vegetation.  This  consists  of  an  open 
growth  of  salt-grass,  Distichlis  spicata,  which  is  frequently  mixed  with  a 
sparse  growth  of  Agropyrum  pseudorepens  (plate  6b).  In  places  occur  scat¬ 
tered  plants  of  Poa  pratensis;  other  species,  especially  of  forbs,  are  practically 
excluded.  Agropyrum  is  much  dwarfed,  and  with  Distichlis  forms  a  layer 
seldom  exceeding  5  to  8  inches  in  height.  The  sparse  flower-stalks  are  only 
8  or  10  inches  high,  and  consequently  light  plays  a  minor  role  in  deciding  the 
fate  of  transplants. 


Behavior. 

The  same  species  as  in  the  case  of  the  low  prairie  and  from  the  same 
sources  as  before,  were  transplanted  into  the  salt-flats,  with  the  exception  of 
Bulbilis.  Andropogon  furcatus,  A.  scoparius,  and  Panicum  virgatum  had  been 
transplanted  during  the  spring  of  1919.  The  first  season  they  made  a  poor 
growth  and  none  put  forth  flower-stalks;  from  the  outset  in  1920,  Stipa 
appeared  yellow  and  dwarfed.  All  of  the  others  suffered  more  or  less  severely 
during  the  summer  drought.  Late  in  June  nearly  all  showed  more  or  less 
wilting  and  some  yellowing.  In  July  the  ground  was  cracked  on  one  or  more 
sides  of  the  blocks  of  sods,  a  phenomenon  due  to  local  soil  texture  and  one 
which  did  not  occur  elsewhere,  even  in  the  dry  soils  at  Burlington.  However, 
none  of  the  transplants  died.  Compared  with  their  growth  in  the  adjoining 
low  pi  airie,  nearly  all  were  greatly  dwarfed  and  lacked  vigor  and  but  6  of  the 
13  species  blossomed.  These  were  Agropyrum,  Distichlis,  Bouteloua  gracilis, 
Elymus,  Koeleria,  and  Stipa.  The  flower-stalks  were  usually  short  and  the 
inflorescence  smaller  than  normal. 

Swamp  Station. 

Character. 

The  swamp  station  is  located  in  the  valley  at  the  foot  of  a  hill  0.25  mile 
north  of  the  high-prairie  station.  During  1920  water  stood  above  the  soil- 


46 


EXPERIMENTS  DURING  1920. 


level  throughout  April,  May,  and  most  of  June.  For  the  remainder  of  the 
season  the  soil  was  saturated  at  nearly  all  times  to  near  the  surface.  The  vege¬ 
tation  consisted  chiefly  of  a  rank  growth  of  Spartina  cynosuroides,  with  Scirpus 
atrovirens  and  Heleocharis  palustris.  Phalaris  arundinacea  and  relict  Typha 
latifolia,  with  several  species  of  Juncus  and  Carex ,  played  a  minor  role. 
Adjoining  the  wettest  area  and  making  the  transition  to  the  grassland  was  a 
zone  of  almost  pure  Poa  pratensis.  Sods  were  transplanted  into  both  areas. 
In  the  latter  the  water  stood  above  the  surface  during  April  and  May,  while  * 
throughout  much  of  the  remainder  of  the  season  the  soil  was  saturated  or 
nearly  so  almost  to  the  surface.  Vegetation  in  both  areas  grew  rank,  but 
aeration  was  obviously  a  factor  of  equal  or  greater  importance  than  light. 

Behavior. 

Sods  of  the  same  species  used  on  the  low  prairie  were  placed  in  the  wettest 
portion  of  the  swamp  and  in  the  adjoining  Poa  zone  on  April  24.  Water  stood 
on  the  surface  of  the  swamp  until  after  June  15.  By  June  2,  Andropogon 
scoparius  and  Bouteloua  gracilis  had  died,  and  the  leaf-tips  were  dead  on 
A.  furcatus,  Elymus,  and  Stipa,  while  Koeleria ,  which  was  heading  out  at  4 
to  8  inches  high,  had  most  of  its  leaves  dead.  Spartina  and  Panicum  were 
thriving.  By  the  middle  of  June  the  whole  area  was  badly  overgrown. 
Heleocharis  had  reached  a  height  of  20  and  Scirpus  atrovirens  30  inches,  while 
both  Poa  and  Spartina  overtopped  all  the  transplants.  Light  values  ranged 
from  2  to  10  per  cent.  Bouteloua  racemosa  had  died  and  Stipa  was  nearly 
dead.  The  basal  leaves  on  Agropyrum  and  Elymus  had  died,  on  the  latter  to 
a  height  of  9  inches,  and  Distichlis  was  much  attenuated.  The  flower-stalks  of 
Koeleria  had  rotted  off  at  the  base  and  only  a  few  green  leaves  remained. 
Koeleria ,  Stipa,  A.  furcatus,  and  A.  nutans  completed  the  mortality  list  for  the 
first  season.  Spartina  had  flower-stalks  5  feet  tall.  A  few  poor,  slender  plants 
of  Agropyrum,  Distichlis,  Poa,  and  better  ones  of  Panicum  survived.  The 
stems  of  Elymus  rotted  off  near  the  ground,  but  new  shoots  came  out  from  the 
base.  Panicum  did  not  seed.  The  other  survivors,  except  Spartina,  had 
gone  through  a  period  of  anthesis  earlier  in  the  season. 

Aside  from  a  deficit  of  oxygen,  low  light  intensities  must  be  considered  in 
accounting  for  these  results.  During  July  and  August  a  dense  growth  of  Spar¬ 
tina,  Scirpus,  Phalaris,  etc.,  to  a  height  of  4  feet  or  more  so  completely  over¬ 
shadowed  the  transplants  that  they  were  found  with  difficulty,  and  light 
values  ranged  between  1.8  and  7.5  per  cent.  Transplants  in  the  Poa  zone 
grew  under  slightly  less  unfavorable  conditions  in  regard  to  both  deficient 
aeration  and  reduced  light.  However,  Andropogon  scoparius  and  A.  nutans 
both  died  in  May  and  Koeleria  and  Stipa  in  July.  Some  of  the  other  species 
had  dead  basal  leaves  and  were  more  or  less  attenuated.  All  of  the  survivors 
except  A.  scoparius,  A.  furcatus,  Bouteloua  gracilis,  and  B.  racemosa  produced 
seed. 

Sods  of  Stipa  setigera  and  S.  eminens  from  California  were  transplanted  to 
both  high  and  low  prairie  on  April  27.  They  were  watered  from  time  to  time 
as  necessary.  During  May  and  early  June  all  showed  slight  to  fair  growth,  but 
by  July  15  three  had  died  at  each  station  and  the  others  were  growing  poorly. 
All  had  died  on  the  high  prairie  by  August  9,  while  only  one  of  each  species 
survived  on  the  lowland.  The  leaves  on  these  did  not  exceed  2  or  3  inches  in 


SUMMARY. 


47 


height.  They  remained  alive  until  fall,  when  they  were  winterkilled.  Sods 
of  several  species  from  Arizona  were  transplanted  into  high  prairie  on  June  2 
and  were  also  watered  from  time  to  time.  By  June  15  some  plants  showed 
a  new  growth,  but  a  month  later  half  of  them  were  dead  and  the  others  were 
doing  poorly.  These  died  during  August,  with  the  exception  of  a  single  Bou- 
teloua,  which  produced  a  flower-stalk  20  inches  high;  however,  this  plant  was 
winterkilled. 


Summary. 

Experiments. 

A  summary  of  the  planting  experiments  is  given  in  table  17.  Omitting 
the  data  from  Colorado  Springs,  where  the  plants  were  watered,  the  per¬ 
centage  of  germination  was  greatest  at  Nebraska  City  and  in  the  low  prairie 
at  Lincoln,  as  was  also  that  of  establishment,  if  the  cultivated  area  is  omitted. 
Establishment  was  lowest,  15  per  cent,  on  the  gravel-knoll.  Of  the  species 
which  frequently  failed  to  germinate,  Aristida  failed  at  6  places  of  planting, 
Bouteloua  hirsuta,  B.  gracilis,  Koeleria ,  and  Liatris  at  2  or  3  each,  and  Andro- 
pogon  scoparius  at  1.  Andropogon  nutans  grew  in  9  of  the  10  places  sown; 
A.  scoparius,  Elymus,  and  B.  hirsuta  in  6,  while  Koeleria  and  Stipa  viridula 
grew  in  4  of  5.  In  general,  the  percentage  of  germination,  as  well  as  that  of 
establishment,  increased  from  surface  to  trench  to  quadrat,  and  inversely 
with  competition  for  water  and  light. 


Table  17. — Summary  of  planting  experiments ,  1920. 


P. 

ct.  of  species  germinating. 

P. 

ct.  of  germinated  species 
established. 

r 

Method  of 
planting. 

Gravel- 

knoll. 

Low 

prairie. 

Cultivated 

land. 

Nebraska 

City. 

Colorado 

Springs. 

Gravel- 

knoll. 

Low 

prairie. 

Cultivated 

land. 

Nebraska 

City. 

Colorado 

Springs. 

Surface . 

75 

80 

33 

• 

50 

Trench . 

71 

57 

67 

100 

30 

100 

100 

60 

Denuded  quadrat. . 

71 

100 

100 

56 

0 

91 

100 

80 

Average . 

71 

77 

67 

93 

56 

15 

75 

100 

70 

80 

Including  with  these  data  those  from  the  high  prairie  at  Lincoln,  Phillips- 
burg,  and  Burlington,  and  arranging  the  stations  in  order  of  the  average  per¬ 
centage  of  germination  under  the  different  methods  of  sowing,  the  sequence  is 
that  shown  in  column  1  of  table  18.  Column  2  gives  the  arrangement  based 
on  the  percentage  of  the  germinated  species  that  became  established,  the 
low-prairie  station  ranking  ahead  of  Nebraska  City.  The  difference  between 
the  percentage  of  germination  in  high  and  low  prairie  is  much  less  than  the 
difference  in  that  of  establishment.  The  use  of  the  most  favorable  method  of 
planting,  i.  e.,  the  denuded  quadrat,  gives  practically  the  same  sequence  of 
stations. 


48 


EXPERIMENTS  DURING  1920. 


Table  18. — Comparison  of  germination  and  growth  at  all  stations}  1920. 


Average  per  cent  of 
germination. 

Average  per  cent  of 
establishment. 

Per  cent  of  establish¬ 
ment  in  denuded  quadrats. 

Nebraska  City .  93 

High  prairie,  Lincoln. ...  86 

Phillipsburg .  80 

Low  prairie,  Lincoln ....  77 
Gravel-knoll,  Lincoln. ...  71 
Burlington .  38 

Low  prairie .  75 

Nebraska  City .  70 

High  prairie .  42 

Phillipsburg .  33 

Burlington .  25 

Gravel-knoll .  15 

Nebraska  City . 100 

Low  prairie .  91 

High  prairie .  80 

Phillipsburg .  67 

Burlington .  43 

Gravel-knoll .  0 

In  accounting  for  the  above  results,  it  remains  only  to  compare  the  habitats 
at  Nebraska  City,  low  prairie,  and  gravel-knoll  a  little  more  fully.  Those  of 
the  high  prairie  (Lincoln),  Phillipsburg,  and  Burlington  have  already  been 
shown  to  decrease  in  all  conditions  favorable  for  plant  growth  in  the  order 
mentioned. 

Physical  Factors. 

A  comparison  of  the  holard  at  the  gravel-knoll  and  Burlington  stations  shows 
that  it  is  not  greatly  different,  both  very  frequently  falling  to  the  hygroscopic 
coefficient  (tables  12  and  6).  In  the  first  6  inches  especially  it  is  often  reduced 
by  surface  evaporation  to  even  a  lower  point.  The  erosion  of  the  soil  about 
the  seedlings  was  often  pronounced  on  the  gravel-knoll  and  in  this  respect 
growth  conditions  were  less  favorable  than  at  Burlington.  The  cover  of  short- 
grasses  on  both  areas  indicates  xerophytic  conditions,  the  vegetation  often 
drying  and  turning  brown  late  in  July  or  in  August.  The  chresard  was  con¬ 
tinuously  higher  on  low  than  on  high  prairie,  a  difference  of  5  or  10  per  cent 
in  favor  of  the  former  not  being  unusual.  The  low  prairie  was  also  better 
supplied  with  water  than  the  Nebraska  City  station,  though  the  hygroscopic 
coefficient  wras  at  no  time  reached  in  either  habitat,  a  margin  of  3  to  10  per 
cent  or  more  at  all  depths  usually  being  present.  The  average  daily  evapora¬ 
tion  was  also  slightly  less  in  the  low  prairie,  Nebraska  City  being  intermediate 
between  the  low  and  high  prairie  stations  at  Lincoln  (fig.  19). 


Fig.  19. — Average  daily  evaporation,  high  prairie  (solid  line), 
and  low  prairie,  Lincoln  (short  broken  lines),  and  Ne¬ 
braska  City  (long  broken  lines),  1920. 


However,  a  comparison  of  the  average  weekly  humidity  at  these  three 
stations  shows  this  to  be  much  higher  at  Nebraska  City  (68  to  82  per  cent) 
than  on  the  low  prairie  (57  to  79  per  cent),  the  high  prairie  being  lowest  of  all 
(58  to  73  per  cent).  The  average  weekly  humidity  at  the  three  stations  was 


i  EXPERIMENTS. 


49 


73. S.  71.9.  and  65  .4  respectively  from  June  3  to  August  26.  This  factor  seems 
suffi  cient  to  account  for  Nebraska  City  exceeding  the  low- -prairie  station  both 
in  per  cent  of  germination  and  of  establishment  in  denuded  quadrats. 

In  summary,  two  sod  transplants  died  from  drought  on  the  gravel-knoll 
All  showed  repeated  rotting  and  dying  back  of  the  leaves,  including  those 
Altered  from  time  to  time,  and  the  hve  which  blossomed  did  so  earlier  than 
elsewhere.  Drying  at  the  base  was  often  quite  as  pronounced  as  at  Burlington. 
AH  of  the  transplants  nourished  on  the  low  prairie  and  all  but  Spcrtina  blos¬ 
somed.  On  the  salt-fats  the  transplants  suffered  more  or  less  severely  during 
drought,  as  shown  by  the  wilting  and  yellowing  of  leaves.  None  died,  but  all 
were  considerably  dwarfed.  The  dower-stalks  were  short  on  the  species  that 
blossomed  and  the  inflorescence  smaller  than  normal.  The  sods  in  the  swamp 
suffered,  from  deficient  aeration  especially  and  also  from  deficient  light.  Five 
high-prairie  species  and  two  from  the  lew  prairie  died.  All  but  Spcmbu  and 
Paver--.  . .  umr..-  .  shewed  the  erects  of  deficient  aeration,  the  basal  leaves  of 

c* 


several  clams  dying  and  the  rower-stalks  rotting  off  rear  the  base.  Sir  of  the 
13  produced  seed,  some  or  much  abbreviated  rower-stalks.  Sods  in  the  Pckl 
core  cd  the  swamp  fid  somewhat  better,  only  three  high-prairie  and  one  low- 
prairie  steedes  succumbing  two  other  high-prairie  species  failed  to  dower. 
N  earlv  ah  sh;wed  the  erects  of  deficient  aeration  and  shade,  but  to  a  less 


degree  than  those  in  the  swamp.  The  transplants  at  Colorado  Springs  were 
made  late  in  the  season  -June  9  and  watered  at  intervals :  ah  survived,  but 

nine  made  a  good  growth. 


Exseeimests  Dueixg  1918  no  1919. 

*><~v  Of  19  IS 

Feme  preliminary  experiments  were  conducted  during  1918  ani  1919.  and 
an  account  of  the  results  seems  desirable  for  the  sake  of  completeness.  On 
April  6.  seeds  of  the  following  species  were  sown  in  4-inch  pots  in  rich  loam 
soil  in  the  greenhouse:  .irrm^  rkucmn.  A odr?poeeri  / urcatu.?.  A.  rerun?. 
A.  sc&parius.  Aristide  oLi.;nr.tha .  Baiticloua  h: mru .  and  8yer>:o.  ae  osper. 
When  the  roc-ts  had  reached  a  depth  of  3  to  5  inches  ani  the  plums  were  wed 
established,  the  latter  were  transferred  to  trenches  S  inches  wide  and  6  inches 
deep.  This  was  done  on  April  26  in  both  gravd-knoll  and  high  prairie.  4  to 
14  pets  cf  each  species  being  transplanted  at  each  station.  They  were  wmered 
from  time  to  time  until  June  1.  when  they  were  f. rally  weeded  and  given  no 
further  attention  until  late  in  September.  On  October  25  to  27  the  plants 
were  counted,  the  roots  excavated,  and  measurements  taken.  Tne  summer 
was  exceedingly  dry  and  only  one  plant,  eye  uve  .  survived  on  tne  gravei- 
knoiL  In  the  high  prairie  all  of  the  An  skim  died,  ad  but  one  of  Amcymivu, 
and  over  half  of  fkrceiovu  and  ep-sr;eol.-?.  while  only  tne  trree  species  of 
Ardmpceon  came  through  with  small  mortality. 

Fci.reTu.u  t  ecu  had  reached  an  average  height  of  6.5  inches  and  most  of 
the  plums  had  seeded.  The  bulk  of  the  root  system  plate  was  in  tne 
drst  S  inches  of  soil,  although  seme  roots  penetrated  considerably  deeper. 
A  frycc  T ■verne  attained  a  height  of  5  or  6  Irenes  and  the  coarse  roots 
were  traced  well  below  the  18-inch  level:  A.  scope: rim  was  c  to  10  inches  tall; 
the  central  plant  in  plate  9a  shews  the  major  portion  of  me  root  system,  tne 
roots  being  much  utter  and  mere  abundant  than  in  the  preceding  species. 


50 


EXPERIMENTS  DURING  1920. 


A.  nutans  grew  to  a  height  of  7  or  8  inches  (plate  9a).  The  largest  of  the  three 
survivors  of  Sporobolus  asper  reached  a  height  of  10  inches,  the  plants  were 
in  seed,  and  the  roots  penetrated  more  than  15  inches,  the  lateral  spread 
reaching  distances  of  8  to  10.5  inches.  The  difficulty  of  extracting  the  entire 
root  system  in  grassland  has  already  been  mentioned.  Because  of  competition 
the  shoot  growth  was  less  than  in  cultivated  soil,  and  it  seems  probable  that 
the  root  system  was  also  shortened.  These  root  systems,  which  were  only 
partially  recovered,  afford  a  striking  contrast  to  those  of  similar  species  of  a 
single  year’s  growth  in  cultivated  soil  (p.  35  and  36). 

Season  of  1919. 

During  1919,  Andropogon  furcatus  was  sown  in  quadrats  on  May  10  and 
again  on  June  15  in  high  prairie,  low  prairie,  gravel-knoll,  and  in  the  lower 
cultivated  plats.  Those  on  the  high  prairie  which  were  watered  on  May  28  at 
the  same  time  as  the  others,  did  very  well,  and  little  difference  was  noted  be¬ 
tween  the  two  plantings.  In  June  1920,  both  quadrats  contained  plants  6  to  8 
inches  tall,  which  reached  7  to  10  inches  by  fall,  but  no  flower-stalks  appeared. 
A  good  sod,  almost  merging  into  the  native  prairie,  was  developed  during  1921, 
but  no  species  flowered.  By  June  1922,  some  invasion  had  occurred,  and 
later  in  the  season,  as  well  as  in  1923,  flower-stalks  were  produced,  although 
rather  sparsely.  Those  on  the  low  prairie  made  a  better  growth  the  first 
season,  but,  because  of  the  plowing  of  the  area,  were  transplanted  to  salt-flat 
and  the  new  low-prairie  station  the  following  spring.  Both  lots  continued  to 
thrive  (pp.  44  and  45).  Plantings  of  this  same  species  on  the  gravel-knoll 
died  the  first  season  or  the  following  winter.  Those  made  in  the  lower 
cultivated  plats  did  best  of  all.  The  roots  of  the  plants  were  excavated  on 
August  26,  when  they  had  a  working  depth  of  2  feet  and  a  maximum  depth  of 
over  3  feet  (plate  9b).  A  few  stalks  flowered  and  set  seed.  The  vegetative 
growth  by  August  of  the  second  season  was  2  feet  high.  Flower-stalks,  some 
of  which  were  44  inches  tall,  occurred  in  abundance  and  good  seed  was 
developed. 

When  about  3  weeks  old,  duplicate  seedlings  of  Aristida  purpurea,  Stipa 
viridula,  and  Elymus  canadensis  were  transplanted  in  the  usual  way  on 
May  5,  into  high  and  low  prairie,  gravel-knoll,  and  upland  and  lowland 
cultivated  areas.  Bouteloua  racemosa  was  also  included  in  the  last  two  sta¬ 
tions.  All  of  those  on  the  gravel-knoll  died  before  the  end  of  August,  after 
repeated  wilting  and  drying  throughout  the  summer.  Those  on  the  low 
prairie  grew  well  until  fall,  but  were  plowed  up  the  following  spring.  On  the 
high  prairie  all  lived  through  the  first  season,  but  did  not  survive  the  winter. 

Aristida  and  Stipa  both  died  on  the  cultivated  upland,  while  Bouteloua  and 
Elymus  made  an  excellent  growth  and  were  in  full  bloom  August  1.  By  August 
15,  Bouteloua  had  reached  a  height  of  23  inches  (plate  4b).  Clumps  of  Elymus 
1.5  to  2  inches  in  diameter  at  the  base  were  common,  and  as  many  as  66  stalks 
were  counted  in  a  single  clump.  The  dense  root  system  (plate  4a)  reached  a 
depth  of  2  feet  and  a  maximum  lateral  spread  of  22  inches. 

All  the  plants  grew  very  well  in  the  lower  cultivated  plots,  except  Aristida, 
wdiich  did  rather  poorly.  Bouteloua  came  into  full  bloom  late  in  August,  after 
making  an  excellent  vegetative  growth,  and  it  matured  seed  abundantly. 
Elymus  also  blossomed,  and  by  August  9  of  the  second  season  had  flower- 


SOD  TRANSPLANTS. 


51 


stalks  58  inches  tall  with  very  large  spikes.  Stipa  viridula  made  an  excellent 
growth,  but  did  not  seed  until  the  next  year.  By  August  9,  1920,  the  seed  was 
ripening  on  flower-stalks  over  5  feet  tall  and  in  spikes  14  inches  in  length. 
The  root  system  at  this  time  had  reached  a  depth  of  over  5  feet  and  had  a 
lateral  spread  of  18  to  20  inches  near  the  surface.  Roots  were  very  abundant 
to  2  feet.  In  fact,  the  fine  growth  and  great  size  attained  by  native  species 
under  favorable  conditions  emphasize  the  controlling  effects  of  competition  in 
the  native  grassland. 

Sod  Transplants. 

Gravel-knoll. 

The  following  sods  were  transplanted  to  the  gravel-knoll  during  the  spring 
of  1919:  Agropyrum  glaucum,  Andropogon  furcatus,  Bulbilis  dactyloides, 
Ely?nus  canadensis ,  Koeleria  cristata,  and  Panicum  virgatum.  They  were 
watered  a  few  times  until  established.  Agropyrum,  Bulbilis,  Elymus,  and 
Koeleria  all  blossomed  somewhat  earlier  than  elsewhere,  the  flower-stalks 
being  somewhat  dwarfed.  During  July  all  dried  out  badly,  A.  furcatus  and 
Koeleria  dying  by  the  end  of  the  season.  Four  sandhill  dominants,  Andropogon 
halli,  Calamovilfa  longifolia,  Muhlenbergia  pungens,  and  Sporobolus  cryptan- 
drus,  were  secured  from  the  extra-regional  sandhills  near  Central  City, 
Nebraska,  and  transplanted  into  the  high  prairie  on  June  9.  Great  difficulty 
was  encountered  in  holding  the  sand  in  place  about  the  root  systems.  The 
new  shoot  growth  was  clipped  back  as  usual  to  lessen  transpiration,  but  in 
spite  of  repeated  watering,  none  survived. 

Table  19. — Holard  in  excess  of  hygroscopic  coefficient  on  the  gravel-knoll,  1919. 


Date. 

0  to  0.5 
foot. 

0.5  to  1 
foot. 

1  to  2 
feet. 

2  to  3 
feet. 

3  to  4 
feet. 

Apr.  28 . 

24.0 

25.3 

20.5 

19.0 

12.0 

May  10 . 

7.3 

5.6 

7.1 

7.9 

1.1 

May  27 . 

1.0 

1.7 

3.6 

•  •  •  • 

«  •  •  • 

June  16 . 

7.0 

6.6 

.... 

•  •  «  • 

.... 

July  1 . 

0.2 

0.1 

•  •  •  • 

.... 

.  .  .  . 

July  8 . 

-1.1 

-0.4 

2.4 

3.5 

•  •  •  • 

July  14 . 

-1.7 

-0.1 

•  •  •  • 

.... 

.... 

July  28 . 

1.6 

1.7 

6.7 

11.4 

7.1 

Aug.  26 . 

-0.7 

6.6 

7.2 

6.7 

7.1 

Sept.  6 . 

Hygroscopic 

-0.9 

-0.5 

0.4 

4.1 

8.3 

coefficient. 

5.2 

4.9 

3.1 

2.8 

7.4 

An  examination  of  the  rainfall  records  shows  that  while  May  and  June  had 
ample  rainfall,  July  was  extremely  dry.  The  total  rainfall  was  only  0.38  inch 
(normal  3.83  inches),  0.30  inch  of  which  fell  on  the  last  day  of  the  month. 
The  rainfall  for  August  was  also  an  inch  below  normal.  The  low  holard  of  the 
gravelly  soil  in  which  the  plants  were  growing  is  shown  in  table  19.  On  July  14 
the  native  grama  grasses  ( Bouteloua  gracilis  and  B.  hirsuta)  began  to  dry 
badly  and  two  weeks  later  all  were  brown  and  cured  on  the  ground. 

During  1920,  which  was  a  more  favorable  season,  Agropyrum  produced  a 
thin  crop  of  flower-stalks  34  inches  high,  while  Bulbilis  flowered  profusely  and 
put  forth  numerous  stolons  8  to  12  inches  long,  some  of  which  rooted  in  the 


52 


EXPERIMENTS  DURING  1920. 


grama  sod.  Only  2  stalks  of  Elymus  about  a  foot  tall  were  left;  Panicum 
did  poorly,  reaching  a  height  of  but  12  to  14  inches.  Undoubtedly  by  this 
time  most  of  these  species  were  rooted  rather  deeply  in  the  clay  subsoil  at 
about  4  feet  depth.  In  1921,  Agropyrum  again  blossomed,  but  not  profusely, 
while  Bulbilis  seemed  quite  at  home,  blooming  luxuriantly  and  extending  its 
territory  nearly  a  foot  into  bare  areas.  One  of  the  two  stems  of  Elymus  put 
forth  a  flower-stalk  at  18  inches  height;  Panicum  remained  dwarfed  (13  inches) 
and  did  not  blossom.  During  1922  all  made  an  excellent  growth,  exeept 
Elymus,  which  was  winterkilled.  As  usual,  Agropyrum  blossomed  early; 
Bulbilis  had  spread  until  it  occupied  nearly  twice  its  original  area,  and 
Panicum  flowered  at  18  to  24  inches.  All  dried  earlier  in  the  late  summer 
than  elsewhere,  owing  to  the  severe  drought  in  August.  The  next  year  was 
an  excellent  one  for  growth,  and  Agropyrum  spread  over  30  inches  into  the 
adjacent  grassland,  flowering  profusely  at  2.5  to  3  feet.  Bulbilis  spread 
even  more  widely  than  before,  but  the  stolons  rooted  with  difficulty  in  the 
heavy  growth  of  grasses;  it  also  flowered  profusely.  Panicum  likewise 
increased  its  area  slightly,  but  blossomed  at  a  height  of  only  27  inches. 

Low  and  High  Prairie. 

The  same  species,  except  for  Panicum  and  Andropogon  furcatus,  but  in¬ 
cluding  A .  scoparius  and  Stipa  spartea,  were  transplanted  to  the  low  prairie 
during  April  and  early  May  1919.  All  flourished  and  bloomed  profusely 
except  Stipa.  No  further  data  were  obtained,  since  this  part  of  the  prairie 
was  broken  the  following  spring.  A  similar  lot  of  sods,  with  the  addition  of 
Bouteloua  gracilis  from  the  gravel-knoll  and  Panicum,  Poa,  Andropogon 


Fig.  20. — Average  daily  evaporation  on  high  prairie  (upper  line)  and  low 

prairie  (lower  line),  1920. 


furcatus,  and  Spartina  from  the  low  prairie,  were  transplanted  to  high 
prairie.  Because  of  the  severe  drought  during  July,  the  transplants  wilted 
somewhat  and  both  the  production  and  size  of  flower-stalks  and  inflorescence 
were  reduced.  The  chresard  on  both  high  and  low  prairie  is  given  in  table  20. 

The  high  evaporation  rate  (daily  average  30  to  50  c.  c.)  on  the  high  prairie 
during  the  drought  period,  and  the  relatively  lower  one  on  low  prairie  (15  to 
28  c.  c.),  together  with  the  evaporation  throughout  the  season,  are  compared 


SOD  TRANSPLANTS. 


53 


in  figure  20.  Greater  wind  movement  at  the  upper  station  was  an  important 
factor  in  causing  the  difference  in  evaporation,  although  humidity  played  a 
large  share  also.  From  July  7  to  August  18  the  average  daily  evaporation 
was  64  per  cent  greater  at  the  upland  station. 


Table  20. — Holard  in  excess  of  hygroscopic  coefficient  on  high  and  low  prairie  at  Lincoln ,  1919. 


High  prairie. 

Low  prairie. 

Date. 

0  to  0.5 
foot. 

0.5  to  1 
foot. 

1  to  2 
feet. 

2  to  3 
feet. 

3  to  4 
feet. 

0  to  0.5 
foot. 

0.5  to  1 
foot. 

1  to  2 
feet. 

2  to  3 
feet. 

3  to  4 
feet. 

Apr.  28 . 

May  5 . 

18.5 

19.8 

22.2 

18.2 

19.1 

15.6 

13.8 

9.8 

11.4 

14.2 

24.4 

26.1 

26.5 

17.3 

16.1 

17.5 

16.1 

19.5 

May  27 . 

8.2 

13.7 

11.2 

.... 

.... 

8.8 

17.8 

16.4 

.... 

.... 

June  16 . 

16.6 

16.6 

.... 

.... 

.... 

24.5 

18.6 

.... 

.... 

July  1 . 

11.5 

10.0 

9.5 

9.9 

10.0 

11.7 

11.1 

17.1 

17.1 

18.5 

July  8 . 

2.3 

5.3 

9.2 

10.7 

9.2 

5.4 

5.7 

16.8 

17.1 

20.6 

July  14 . 

0.0 

3.5 

5.2 

.... 

.... 

4.4 

5.6 

9.6 

.... 

.... 

July  28 . 

-0.6 

1.2 

1.6 

7.1 

11.1 

0.1 

1.9 

5.1 

13.3 

18.5 

Aug.  11 . 

4.4 

2.0 

2.0 

3.3 

7.0 

6.8 

3.6 

5.9 

8.1 

18.1 

Aug.  26 . 

10.4 

3.2 

2.2 

5.4 

5.4 

17.2 

6.1 

7.3 

8.9 

17.9 

Sept.  6 . 

1.2 

3.3 

3.4 

5.6 

8.3 

-0.2 

4.4 

2.6 

9.3 

18.9 

Sept.  26 . 

14.5 

15.0 

5.2 

2.6 

5.7 

17.2 

15.2 

5.8 

10.0 

16.2 

Hygroscopic  coef- 

ficient . 

9.5 

8.7 

8.6 

7.1 

6.2 

11.8 

11.1 

10.3 

10.2 

11.9 

June 

.23  30 

7 

July 

14 

21 

28 

4 

August 

11  18 

25 

Sept 

1  8 

Fig.  21. — Average  day  and  night  temperature  at  Lincoln  (solid  lines),  and  Colorado 

Springs  (broken  lines),  during  1919. 

Thermograph  records  of  soil  temperature  at  the  two  stations  at  a  depth  of  6 
inches  show  no  marked  differences.  The  daily  range  at  the  lowland  station 
was  usually  4°  to  7°  F.;  in  the  drier  soil  of  the  upland  station  4°  to  12°  F. 
The  minimum  soil  temperatures  were  2°  or  3°  F.  lower  at  the  former  station  and 
the  maximum  3°  to  9°  F.  higher  on  the  upland.  The  soil  temperatures  varied 
from  53°  F.  (average  60°  to  65°  F.)  late  in  May,  to  85°  F.  (average  70°  to  78°  F.) 
in  August.  Except  in  early  spring,  when  the  low  temperatures  on  the  lower 


54 


EXPERIMENTS  DURING  1920. 


wetter  soil  may  retard  growth,  and  the  higher  temperatures  at  all  depths  on  the 
upland  may  facilitate  absorption,  it  is  not  probable  that  the  effects  of  tempera¬ 
ture  on  the  development  of  vegetation  at  the  two  stations  are  very  different. 
A  comparison  of  the  two  sets  of  thermograph  records  shows  that  differences  of 
air-temperature  greater  than  5°  F.  are  rare  at  the  two  stations.  It  seems  cer¬ 
tain  that  such  small  differences  in  temperature  variations  in  the  range  of 
growth  conditions  (minimum  65°  F.  late  in  May,  maximum  105°  F.  in  July  and 
August)  would  be  almost  negligible  in  the  development  of  natural  grassland. 
The  average  day  and  night  temperatures  throughout  the  season,  together  with 
those  at  the  Colorado  Springs  station,  are  compared  in  figure  21  and  the 
average  daily  evaporation  rates  at  the  same  station  in  figure  22.  Notwith¬ 
standing  the  adverse  conditions,  all  the  transplants,  including  Spartina , 
bloomed  more  or  less  profusely,  with  the  exception  of  Andropogon  furcalus, 
Koeleria,  and  Stipa. 


Fig.  22. — Average  daily  evaporation  at  Colorado  Springs  (upper  line), 
and  Lincoln  (lower  line),  during  1919. 

During  1920,  all  of  the  transplants  did  quite  well,  except  two  of  the  Stipas 
which  were  not  well  developed.  Bulbilis  made  an  excellent  growth,  blossoming 
profusely  by  the  middle  of  June  (plate  10a),  and  both  Panicum  and  Spartina 
flowered  abundantly  at  heights  of  30  to  44  inches.  In  fact,  Andropogon 
scoparius  and  A.  furcatus  were  the  only  species  that  did  not  blossom,  but  they 
made  a  vegetative  growth  of  8  to  12  inches.  By  the  following  season,  Andro¬ 
pogon  furcatus  had  almost  merged  into  the  common  sod.  Koeleria  was 
nearly  all  dead;  two  of  the  Stipas  were  behaving  normally,  while  the  other 
two  did  not  blossom  and  were  in  very  poor  condition.  Elymus  was  repre¬ 
sented  by  only  one  or  two  stalks,  but  all  of  the  other  species  were  developing 
quite  normally. 

On  August  23,  when  Panicum  virgatum  was  blooming  profusely  with  flower- 
stalks  3  to  4  feet  tall,  a  trench  was  dug  to  a  depth  of  11  feet  and  the  roots  of 
this  3-year-old  transplant  examined.  Below  3  feet  the  silt-loam  soil  became 
more  sandy  and  below  6  feet  it  changed  to  a  sandy  gravel  with  many  small 
rocks.  It  was  quite  moist  at  all  depths.  The  roots  penetrated  to  a  maximum 
depth  of  9.8  feet,  and  were  fairly  abundant  to  7  feet.  The  general  root  habit 
and  branching  were  about  normal  (Weaver,  1920),  but  the  degree  and  extent 
of  branching  were  considerably  more  pronounced  than  in  the  low  prairie. 


SOD  TRANSPLANTS. 


55 


However,  it  did  not  approximate  the  remarkable  network  of  branches  dis¬ 
played  by  this  species  in  the  drier  soils  at  Burlington  (fig.  32). 

Spartina  cynosuroides  was  also  excavated  from  the  same  trench  at  this  time. 
It  had  made  a  good  growth,  notwithstanding  the  rolling  of  leaves  from  time  to 
time  as  a  result  of  drought.  Many  leaves  reached  a  height  of  40  inches.  It 
had  increased  its  area  about  one-third  by  rhizome  propagation,  but  the  root¬ 
stocks  had  not  developed  many  new  shoots.  Roots  were  abundant  to  9  or  10 
feet  and  were  densely  branched  throughout,  perhaps  having  a  third  more 
branches  than  those  in  the  lowland,  and  branches  were  longer  and  rebranched 
to  a  greater  degree  than  those  growing  in  wetter  soil.  Koeleria  and  Poa  died 
during  the  winter  of  1921-22.  The  following  summer  all  the  rest,  except 
Andropogon  scoparius,  made  a  good  growth,  and  flowered  rather  profusely, 
except  the  very  late  bloomers,  which  were  somewhat  retarded  by  the  late 
summer  drought.  Panicum  extended  its  territory  nearly  3  feet,  but  few  of  the 
others  gained  in  area.  During  1923  all  did  very  well,  owing  to  good  growth 
conditions,  Andropogon  furcatus  merging  completely  with  the  native  sod.  All 
flowered  and  set  seed,  the  height  of  the  inflorescence  being  about  normal. 

Mixed  Prairie. 

On  June  19,  1919,  the  following  sods  from  Lincoln  were  transplanted  to 
the  mixed-prairie  station  at  Colorado  Springs:  Agropyrum  glaucum ,  Andro¬ 
pogon  furcatus,  Bulbilis  dactyloides,  Elymus  canadensis  (2  sods),  Koeleria  cris- 
tata  (3  sods),  Panicum  virgatum,  Poa  pratensis,  and  Stipa  spartea  (3  sods). 
Before  planting,  the  hollow  made  for  each  sod  was  filled  with  water  that  was 
allowed  to  sink  away  before  the  sod  was  planted,  tamped  in  place,  and  again 
watered.  Owing  to  watering  at  2-week  intervals,  all  did  fairly  well  the  first 
season.  In  June  1920,  cattle  broke  in  and  closely  grazed  the  entire  fenced 
area.  However,  most  of  the  sods  lived  throughout  the  Season,  but  made 
a  poor  growth,  Bidbilis  and  Agropyrum  alone  coming  into  blossom.  One 
Elymus  and  one  Koeleria  died  late  in  the  summer.  During  1921,  perhaps 
as  a  result  of  repeated  grazing,  the  remaining  Elymus  and  the  two  remain¬ 
ing  koeierias  died,  as  did  also  one  of  the  stipas;  Bulbilis  alone  came  into  blos¬ 
som.  The  area  was  grazed  again  in  1922.  This  repeated  grazing,  combined 
with  drought,  resulted  in  a  very  poor  growth,  Poa  succumbing  and  Bulbilis 
alone  blossoming.  Because  of  further  grazing  in  1923,  it  was  clearly  evident 
that  most  of  the  plants  (except  Bulbilis)  were  rapidly  losing  ground,  Agropyrum, 
Panicum,  and  Andropogon  furcatus  being  represented  by  remnants  only. 


3.  EXPERIMENTS  DURING  1921. 

PHYSICAL  FACTORS. 

Rainfall. 

The  season  of  1921  at  Lincoln  was  quite  favorable  as  to  precipitation. 
Rainfall  for  April,  June,  and  July  was  slightly  above  normal,  while  August 
was  slightly  below  normal,  as  was  May  also  (fig.  9).  An  examination  of  the 
records  shows  that  the  showers  were  exceptionally  well  distributed,  no  marked 
drought  periods  occurring,  and  at  no  time  did  the  vegetation  become  dry  or 
brown,  even  on  the  gravel-knoll. 

At  Phillipsburg  an  excess  of  0.14,  0.98,  and  1.30  inches  fell  during  April, 
May,  and  June  respectively.  The  July  precipitation  was  slightly  above 
normal  and  that  of  August  and  September  slightly  below  (fig.  15).  A  drought 
period  occurred  between  June  9  and  28,  during  which  time  no  efficient  mois¬ 
ture  fell.  At  Burlington  the  precipitation  for  April  was  nearly  twice  normal 
(and  0.86  inch  more  than  at  Lincoln).  May  fell  0.91  inch  below  normal; 
June  was  somewhat  above  (0.58  inch) ;  July  had  less  than  half  the  usual  amount 
(only  1.15  inches);  August  had  an  excess  of  1.19  inches,  but  September  a 
deficit  of  more  than  one-half  the  normal  (fig.  16).  No  efficient  rainfall  oc¬ 
curred  (i.  e.,  showers  of  over  0.15  inch)  between  March  7  and  April  15,  April 
17  and  May  19,  June  22  and  July  4,  and  July  8  and  August  7.  By  July  24 


Fig.  23. — Average  daily  evaporation  at  Burlington  (short  broken  lines),  Phil¬ 
lipsburg  (long  broken  lines),  and  Lincoln  (solid  line),  1921. 

J 

the  short-grasses  were  about  half-dried  and  brown,  while  two  weeks  later 
not  only  the  grama  and  buffalo  grasses  were  curled  and  brown,  but  the  wheat- 
grass  heads  were  dry  as  well. 

Water  Relations. 

The  above  conditions  were  reflected  in  the  holard  at  the  several  stations 
(table  22).  At  Lincoln,  a  margin  of  5  per  cent  or  more  (usually  8  or  10) 


56 


PHYSICAL  FACTORS. 


57 


existed  at  all  times  and  at  all  depths  to  4  feet.  At  Phillipsburg  the  echard 
was  approached  once  in  July  and  twice  in  August,  actually  reaching  the 
danger-mark  to  a  depth  of  4  feet  late  in  that  month.  Conditions  at  Burling¬ 
ton  were,  as  usual,  much  worse.  At  no  time  was  water  available  in  the  third 


Table  21. — Humidity  at  Lincoln  and  Burlington ,  1921. 


For  week  ending — 

Average  day. 

Average  night. 

Average  daily. 

Lincoln. 

Burlington. 

Lincoln. 

Burlington. 

Lincoln. 

Burlington. 

Apr.  21 . 

53.9 

64.7 

59.3 

Apr.  28 . 

53.7 

•  •  •  • 

81.0 

•  •  •  • 

67.3 

.... 

May  5 . 

57.4 

37.0 

86.4 

71.5 

71.9 

54.2 

May  12 . 

57.6 

•  •  •  • 

73.5 

.... 

65 . 5 

•  •  •  • 

May  19 . 

56.1 

.... 

73.9 

.... 

65.0 

•  •  •  • 

May  26 . 

43.7 

,  ,  .  . 

64.2 

.... 

53.9 

•  •  •  • 

June  2 . 

57.2 

39.4 

79.4 

78.7 

67.9 

59.0 

June  9 . 

63.2 

.... 

84.4 

.... 

73.8 

•  •  •  • 

June  16 . 

61.4 

50.4 

81.7 

87.0 

71.5 

68.7 

June  23 . 

61.7 

.... 

80.2 

.... 

70.9 

•  •  •  • 

June  30 . 

60.4 

30.0 

81.7 

72.1 

71.0 

51.0 

J  uly  7 . 

66.0 

50.9 

83.6 

81.0 

73.5 

65.8 

July  14 . 

58.2 

.... 

84.3 

,  .  .  . 

71.2 

.... 

July  21 . 

57.7 

42.5 

80.4 

75.5 

69.0 

59.0 

July  28 . 

63.0 

40.0 

78.4 

78.3 

70.7 

59.1 

Aug.  4 . 

66.7 

38.4 

85.1 

72.6 

75.9 

55.5 

Aug.  11 . 

62.0 

42.8 

81.9 

79.8 

71.8 

61.3 

Aug.  18 . 

65.3 

49.3 

83.4 

83.6 

74.3 

66.4 

Aug.  25 . 

58.0 

.... 

83.4 

.... 

70.7 

.... 

Sept.  1 . 

62.0 

.... 

86.4 

.... 

74.2 

.... 

or  fourth  foot,  while  after  June  30  it  was  depleted  repeatedly  above  the  hard- 
pan  (at  about  2  feet).  A  complete  record  of  humidity  was  not  obtained,  but 
a  comparison  of  the  average  daily  humidity  at  Lincoln  and  Burlington  at 
the  several  intervals  (table  21)  showTs  that  without  exception  the  air  during  the 
day  at  Burlington  was  10  and  often  30  per  cent  less  humid  than  at  Lincoln. 


Fig.  24. — Average  daily  temperature  at  Lincoln  (solid  line),  Phillipsburg  (long  broken  lines),  and  Bur¬ 
lington  (short  broken  lines),  1921. 


58 


EXPERIMENTS  DURING  1921. 


Owing  to  the  lower  night  temperatures  at  Burlington  (altitude  4,160  feet), 
the  humidity  at  this  less  critical  period  averaged  only  slightly  lower  than  at 
the  true-prairie  station. 

Table  22. — Holard  in  excess  of  the  hygroscopic  coefficient  at  the  several 

stations,  1921. 

Lincoln,  Nebraska. 


Date. 

0  to  0.5 
foot. 

0.5  to  1 
foot. 

1  to  2 
feet. 

2  to  3 
feet. 

3  to  4 
feet. 

Apr.  9 . 

20.2 

17.9 

13.7 

13.3 

12.5 

May  18 . 

18.0 

19.7 

16.7 

15.0 

14.5 

May  25 . 

6.2 

13.2 

•  •  •  • 

.... 

•  •  •  • 

June  1 . 

7.9 

10.3 

.... 

.... 

•  •  •  • 

June  7 . 

23.0 

18.6 

14.9 

14.5 

17.2 

June  22 . 

8.8 

14.1 

15.1 

.... 

.... 

June  29 . 

7.0 

8.8 

11.8 

15.2 

■  •  •  • 

July  13 . 

13.4 

20.1 

10.4 

.... 

.... 

July  20 . 

21.0 

18.5 

12.7 

13.1 

16.8 

July  28 . 

7.5 

7.3 

.  .  ,  . 

•  •  •  • 

•  •  •  • 

Aug.  3 . 

10.2 

11.0 

11.3 

.... 

.... 

Aug.  10 . 

16.4 

17.9 

12.0 

12.1 

26.8 

Aug.  23 . 

10.8 

12.9 

8.5 

11.4 

8.8 

Aug.  31 . 

8.5 

7.0 

5.1 

.... 

•  •  •  • 

Hygro.  coeff . 

9.5 

8.7 

8.6 

7.1 

6.2 

Phillipsburg,  Kansas. 

Apr.  28 . 

15.8 

14.5 

11.4 

5.9 

2.3 

May  19 . 

16.8 

13.0 

9.8 

6.4 

0.7 

May  25 . 

12.2 

10.9 

.... 

.... 

.... 

June  9 . 

19.8 

15.8 

13.9 

14.5 

13.0 

June  22 . 

5.3 

8.6 

10.8 

11.7 

9.3 

July  19 . 

1.6 

2.2 

•  •  •  • 

.... 

.... 

July  21 . 

8.2 

3.3 

3.9 

4.6 

•  •  •  • 

July  25 . 

1.6 

2.0 

0.9 

2.7 

4.9 

Aug.  4 . 

3.5 

4.4 

.... 

•  •  •  • 

.  •  •  • 

Aug.  9 . 

0.1 

0.8 

0.6 

2.1 

2.1 

Aug.  17 . 

20.9 

7.5 

1.5 

1.3 

.... 

Aug.  30 . 

-1.6 

-0.4 

-0.6 

0.0 

0.3 

Hygro.  coeff . 

10.6 

10.6 

10.9 

10.6 

10.7 

Burlington,  Colorado. 

Apr.  30 . 

9.6 

10.7 

8.6 

0.0 

1.3 

May  20 . 

6.4 

5.6 

4.7 

-0.7 

-2.2 

June  10 . 

10.3 

0.0 

0.7 

-0.5 

-0.6 

June  30 . 

-2.6 

-1.6 

—  1.5 

-1.0 

-1.3 

July  17 . 

-1.0 

-1.0 

-3.6 

.... 

.... 

July  24 . 

-3.5 

-2.2 

-3.4 

-1.8 

-0.4 

Aug.  8 . 

2.0 

-0.7 

-2.1 

-0.3 

-1.0 

Aug.  17 . 

16.9 

11.7 

-2.4 

-2.0 

.... 

Aug.  29 . 

-0.3 

0.5 

-2.1 

-0.4 

-1.0 

Hygro.  coeff . 

10.9 

10.9 

12.2 

12.0 

11.4 

The  average  daily  evaporation  at  the  several  stations  is  shown  in  figure  23. 
The  rather  uniform  rate  at  Lincoln  (daily  average  8  to  27  c.  c.),  as  compared 
with  the  erratic  and  excessively  high  one  at  Burlington  (18  to  62  c.  c.),  empha- 


PHYSICAL  FACTORS. 


59 


sizes  the  precarious  conditions  for  plant  growth  at  the  latter  station.  Con¬ 
ditions  at  Phillipsburg  were  intermediate  (8  to  43  c.  c.). 

Temperature.  . 

The  average  daily  air-temperature  was  in  general  lowest  at  Burlington, 
while  that  at  Phillipsburg  after  the  third  week  in  June  was  somewhat  higher 
than  at  Lincoln  (fig.  24).  During  May  and  June,  day  temperatures  were 
highest  at  Lincoln  and  lowest  at  Burlington,  but  after  July  1  this  was 
usually  reversed.  Night  temperatures  throughout  the  season  were  distinctly 


Fig.  25. — Average  day  (heavy  lines)  and  night  temperatures  (light  lines),  at  Lincoln  (solid  lines), 
Phillipsburg  (long  broken  lines),  and  Burlington  (short  broken  lines),  1921. 


lower  at  Burlington  by  5°  to  10°  F.,  those  at  the  other  stations  being  very 
similar.  The  soil-temperature  at  a  depth  of  3  inches  was  invariably  lower 
at  Burlington  than  at  Phillipsburg.  Later  in  the  season  soil-temperature  was 
correlated  with  the  holard,  the  soils  becoming  progressively  drier  and  warmer. 
A  series  of  readings  in  cropped  areas  (oat  field)  to  a  depth  of  4  feet  is 
instructive  in  this  connection  (table  23). 


Table  23. — Soil  temperatures ,  1921. 


Depth 

in 

feet. 

April  28- 

30. 

May  19-21. 

June  9-10. 

June  22. 

June  30. 

Lin¬ 

coln. 

Phil¬ 

lips¬ 

burg. 

Bur¬ 

ling 

ton. 

Lin¬ 

coln. 

Phil¬ 

lips¬ 

burg. 

Bur¬ 

ling¬ 

ton. 

Lin¬ 

coln. 

Phil¬ 

lips¬ 

burg. 

Bur¬ 

ling¬ 

ton. 

Lin¬ 

coln. 

Phil¬ 

lips¬ 

burg. 

Bur¬ 

ling¬ 

ton. 

°C. 

°C. 

°C. 

°C. 

°C. 

°C. 

°C. 

°C. 

°C. 

°C. 

°C. 

°C. 

0  to  0.5.  .  . 

15.4 

24.0 

12.0 

21.0 

20.0 

22.2 

22.5 

21.4 

19.8 

21.2 

23.2 

29.2 

0  5  to  1 .  .  . 

13.0 

23.1 

11.0 

19.0 

17.8 

15.0 

21.8 

20.2 

18.8 

21.1 

22.4 

26.1 

1  to  2 . 

12.0 

15.0 

10.5 

13.4 

16.4 

14.0 

20.2 

18.8 

16.8 

20.1 

21.5 

23.9 

2  to  3 . 

12.0 

14.0 

10.5 

13.1 

15.0 

12.4 

18.6 

17.2 

15.8 

18.8 

21.2 

21.8 

3  to  4 . 

10.8 

12.0 

10.0 

12.0 

13.5 

11.8 

17.8 

16.0 

15.0 

17.4 

20.5 

20.0 

60 


EXPERIMENTS  DURING  1921. 


Isolated  readings  at  similar  depths  showed  the  temperature  of  the  grassland 
soil  (below  the  first  foot)  to  be  very  similar  to  that  in  the  cultivated  areas. 

To  summarize;  as  during  1920,  conditions  for  plant  growth  were  much  more 
favorable  at  Lincoln  and  least  favorable  at  Burlington,  while  those  at  Phil- 
lipsburg  were  intermediate,  holard  and  humidity  being  the  controlling  factors. 

PLANTING  RESULTS. 

Surface  Sowing. 

Seeds  of  14  species  were  sown  on  the  surface  of  the  high  prairie  at  Lincoln 
on  April  20.  Aristida  purpurea ,  Elymus  canadensis,  and  Lespedeza  capitata 
failed  to  germinate.  Bouteloua  gracilis,  Koeleria  cristata,  Liatris  punctata, 
and  Sporobolus  asper  germinated  rather  abundantly,  but  died  before  the 
end  of  June,  the  seedlings  being  much  attenuated.  The  light  values  were  low; 
by  May  5  they  fallen  to  16  to  27  per  cent,  as  the  prairie  had  not  been  mown 
the  previous  autumn.  There  was  not  only  considerable  dead  grass,  but  the 
new  growth  was  rank  and  flower-stalk  production  greater  than  usual.  Before 
the  end  of  July,  Bouteloua  hirsuta,  Bromus  inermis  (which  was  badly  eaten 
by  grasshoppers),  Liatris  scariosa,  and  Pinus  ponderosa  were  added  to  the 
mortality  list.  Robinia  pseudacacia  held  out  until  August,  as  did  also  Stipa 
viridula.  Andropogon  nutans  alone  survived  the  season,  making  a  fair  growth 
6  to  9  inches  high  and  becoming  indistinguishable  from  the  native  sod. 

At  Phillipsburg  the  surface  plantings  made  on  April  28  did  very  much 
better,  83  per  cent  living  throughout  the  summer.  After  planting,  showers 
were  opportune  at  both  stations,  all  12  species  germinating  at  Phillipsburg. 
Unquestionably  the  light  relation  was  much  more  favorable  at  the  latter 
station.  Reduced  light  and  surface  drought  were  the  chief  factors  to  which 
plants  gaining  a  foothold  in  climax  grassland  were  subjected.  The  same 
species  as  those  used  at  Phillipsburg,  with  the  addition  of  Sporobolus,  were 
sown  on  the  surface  at  Burlington,  April  30.  None  had  germinated  by  May 
20,  and  only  5  of  the  13  germinated  at  all.  These  were  Bouteloua  racemosa, 
B.  gracilis,  Bromus  inermis,  and  the  two  species  of  Liatris.  All  were  found 
in  greater  or  less  abundance  on  June  10,  but  had  disappeared  by  the  30th. 

The  fate  of  surface-sown  plants  of  the  preceding  year  is  of  interest.  At 
Lincoln  and  Phillipsburg  none  survived  the  first  season.  By  May  of  the  second 
year  at  Burlington,  Bouteloua  gracilis  had  merged  into  the  native  sod.  Stipa 
viridula,  the  other  survivor,  made  a  good  growth  (8  to  10  inches)  and  tillered 
heavily,  standing  out  quite  plainly  in  the  short-grass  turf.  Its  leaves  were 
tightly  rolled  and  somewhat  wilted  from  time  to  time,  and  it  did  not  produce 
flower-stalks.  During  1922  it  grew  vigorously,  but  was  much  smaller  than 
similar  plants  in  denuded  quadrats.  By  the  end  of  the  season  it  was  clear  that 
competition  with  the  native  short-grasses  was  too  severe,  Stipa  rapidly 
losing  ground.  However,  it  held  out  through  the  very  favorable  season  of 
1923,  being  represented  by  only  a  few  culms  6  to  8  inches  high,  while  the  leaves 
of  grama  were  6  inches  tall  all  around  it.  It  was  clearly  evident  that  it  would 
soon  lose  in  the  unequal  struggle. 

Trench  Sowing. 

Although  poor  at  all  stations,  the  results  from  trench  planting  April  20  to 
30  were  best  at  Lincoln.  Of  12  species  used,  all  but  Pinus  ponderosa  germi- 


TRENCH  AND  DENUDED  QUADRATS. 


61 


nated;  Elymus,  Koeleria,  Bromus,  and  Stipa  viridula  succumbed  before 
the  end  of  June,  the  last  two  being  badly  eaten  back  by  grasshoppers. 
The  slender  plants  of  Lespedeza  and  Liatris  punctata,  the  latter  reaching  a 
height  of  5  or  6  inches,  died  in  August.  Andropogon  nutans ,  B.  hirsula,  and 
Sporobolus  came  through  in  excellent  shape,  tillering  heavily  and  forming  a 
rather  dense  sod  from  2  to  6  inches  tall.  Bouteloua  gracilis  was  represented  by 
remnants  only,  and  Liatris  scariosa  by  a  dozen  one-leaved  slender  plants. 

In  the  trench  at  Phillipsburg,  Bouteloua  racemosa ,  B.  gracilis,  B.  hirsuta, 
Koeleria,  Lespedeza,  Liatris  scariosa  and  punctata,  and  Pinus  failed  to  ger¬ 
minate,  while  Bromus  and  Elymus  died  in  June  and  Stipa  viridula  in  July.  A 
single  plant  of  Robinia  pseudacacia  with  5  leaves  and  a  height  of  4  inches  lived 
through  the  summer  but  was  winterkilled.  The  only  species  that  became 
permanently  established  were  Andropogon  nutans  and  Aristida  purpurea; 
the  former  was  represented  in  late  summer  by  4  or  5  good  clumps,  3  tolO  inches 
tall.  Of  the  same  species  sown  in  the  trench  at  Burlington,  Bromus  and  Elymus 
alone  germinated,  and  very  sparsely,  but  both  died  during  the  June  drought. 

The  development  of  the  plants  grown  in  the  1920  trench  at  Lincoln  was 
above  the  average.  During  1921,  Andropogon  nutans,  A.  scoparius,  Bouteloua 
hirsuta,  and  B.  racemosa  all  made  excellent  growth.  The  boutelouas  reached 
heights  of  3  to  8  inches,  and  the  andropogons  of  5  to  10  inches,  the  latter 
forming  a  fairly  dense  sod.  Bouteloua  gracilis  was  represented  by  a  single 
remnant,  which  was  winterkilled.  During  1922  the  four  remaining  species 
made  a  fair  growth,  the  boutelouas  alone  flowering  and  producing  a  single 
flower-stalk  each.  These  grew  well  in  1923,  though  Andropogon  scoparius  and 
Bouteloua  racemosa  were  quite  sparse.  The  height  growth  ranged  from  4  to  14 
inches,  but  none  had  developed  flower-stalks  late  in  August. 

At  Phillipsburg,  Andropogon  scoparius  and  A.  nutans  alone  survived  the 
first  season.  During  1921  they  flourished,  forming  dense  bunches  and  reaching 
heights  of  14  and  24  inches  respectively,  but  they  were  favored  by  some  water 
running  into  the  trench.  A.  nutans  developed  few  flower-stalks.  Both  made 
an  excellent  growth  in  1922,  extending  the  area  of  the  bunches,  but  Andro¬ 
pogon  scoparius  alone  flowered.  In  1923  they  again  grew  rank,  reaching 
heights  of  2  feet,  and  both  flowered  abundantly.  At  Burlington  there  were 
no  survivors  of  trench  sowing. 

Denuded  Quadrats. 

Twenty-eight  species  were  planted  in  the  quadrats  at  Lincoln  (high  prairie) 
on  April  14.  Eight  failed  to  germinate.  Elymus  and  Stipa  viridula  died 
in  June,  Agropyrum  and  Bromus  inermis  in  July,  and  Acer  negundo,  A  sac - 
charinum,  and  Calamovilfa  in  August;  of  these,  Bromus  and  Stipa  were  badly 
damaged  by  grasshoppers;  13  species  survived.  Corylus  americana  and 
Symphoricarpus  spp.,  all  of  which  survived,  were  propagated  at  the  several 
stations  from  rhizomes  obtained  from  Weeping  Water,  Peru,  and  Lincoln, 
Nebraska  rather  than  from  seed. 

Among  the  28  species  planted  in  quadrats  at  Phillipsburg,  9  failed  to 
germinate.  Among  these  were  Koeleria  cristata,  Liatris  scariosa,  Muhlenbergia 
pungens,  and  Onagra  biennis,  none  of  which  germinated  at  Lincoln  and  all  but 
Muhlenbergia  failed  in  the  quadrats  at  Burlington.  Calamovilfa,  Sporobolus 
asper,  and  S.  cryptandrus  died  in  June,  Corylus  and  Pinus  in  July,  while  Stipa 


62 


EXPERIMENTS  DURING  1921. 


viridula  succumbed  in  August.  Except  for  Calamovilfa,  the  losses  here  and  at 
Lincoln  were  of  different  species.  Thirteen  species  survived. 

Of  25  species  planted  on  April  30  at  Burlington,  only  6  did  not  germinate. 
Ten  species  disappeared  in  June,  another  in  July,  and  4  others  in  August, 
Andropogon  nutans,  Calamovilfa  longijolia,  Gleditsia  triacanthus,  and  Stipa 
viridula  being  the  only  ones  to  survive  the  season.  A  comparison  of  the 
growth  of  Gleditsia  and  Andropogon,  the  only  species  that  lived  at  all  three 
stations,  is  instructive.  By  the  end  of  the  summer  the  former  was  4  to 


Fig.  26. — Average  daily  soil-temperature  at  depths  of  3  and  18  inches  respectively  at  Lincoln  (solid 
line),  Phillipsburg  (long  broken  lines),  and  Burlington  (short  broken  lines),  1921. 


8  inches  tall  at  Lincoln  with  12  to  13  leaves  5  to  10  inches  high,  with  the  same 
number  of  leaves  at  Phillipsburg,  and  only  2  to  3  inches  high  with  4  to  6 
leaves  at  Burlington.  Andropogon  had  formed  a  dense  sod  4  or  5  inches  high 
at  Lincoln,  one  12  to  18  inches  high  at  Phillipsburg,  while  at  Burlington  the 
scattered  growth  was  only  2  to  7  inches  in  height. 

Of  the  survivors  in  the  1920  quadrats  at  Lincoln,  Stipa  setigera  and  S. 
eminens  were  winterkilled  (table  58).  Andropogon  nutans  and  A.  scoparius 
flourished,  forming  good  sods  10  to  13  inches  tall,  the  former  having  flower- 
stalks  at  2  feet.  Stipa  viridula  and  Aristida  purpurea  developed  good  bunches 
6  or  7  inches  in  height.  Bouteloua  gracilis  and  Elymus  blossomed,  the  Boute- 
loua  tufts  being  4  to  6  inches  tall  and  those  of  Elymus  12  to  15  inches.  All 
made  a  good  growth  during  1922,  but  Andropogon  scoparius  and  Bouteloua 
gracilis  alone  came  into  blossom,  probably  owing  to  the  severe  drought  in  late 
summer.  None  died  during  the  very  dry  winter  following  (table  58). 

At  Burlington,  only  3  species,  Andropogon  nutans,  Lialris  punctata,  and 
Stipa  viridula,  survived  the  1920  season  in  the  denuded  quadrats.  The 
vicissitudes  of  these  plants  are  of  interest  (table  60) ;  wilting  and  rolling  of  the 
leaves,  dying  back,  and  discoloration  were  of  usual  occurrence.  However, 
they  were  well  rooted  and  all  survived  the  summer  of  1921,  notwithstanding 


DENUDED  QUADRATS. 


63 


the  ravages  of  grasshoppers  and  drought.  In  1922,  all  but  Stipa  viridula 
blossomed.  The  flower-stalks  of  Andropogon  nutans  were  1  to  2.5  feet  high 
late  in  August,  while  Liairis  flowered  profusely.  Stipa  exhibited  many  fine 
clumps  12  to  18  inches  tall  in  1923.  As  in  the  other  quadrats,  its  area  had  been 
scarcely  invaded,  but  it  did  not  blossom.  All  the  species  prospered  and 


seemed  permanently  established,  at  least  as  long 
as  competition  with  the  short-grasses  did  not 
occur  (table  60). 


Root  Development  in  Denuded  Quadrats. 


Fig.  27. — Liatris  punctata  from 
Phillipsburg,  on  July  1  of 
second  year  after  planting. 


From  July  1  to  3  several  species  from  the  1920 
quadrats  at  Phillipsburg  were  excavated  and  the 
root  development  studied.  Liatris  punctata  had 
5  leaves  and  a  height  of  5.5  inches.  The  portion 
of  the  root  which  began  2  or  3  inches  below  the 
surface  was  5  mm.  in  diameter  for  a  distance 
of  about  an  inch,  beyond  which  it  tapered 
rapidly  and  descended  more  or  less  vertically 
downward  to  a  depth  of  nearly  4  feet  (fig.  27).  Nine  branches  came 
off  from  the  tap  in  the  first  8  inches  of  soil,  none  of  which  exceeded  17 
inches  in  length.  Like  the  tap-root,  they  were  fairly  well  supplied  with 
short  branches. 

Bouteloua  hirsuta  formed  fine,  well-tillered  clumps  6  to  9  inches  tall.  The 
root  system  was  characterized  by  its  wide-spreading  habit  in  the  surface  soil. 
The  delicate,  thread-like,  exceedingly  well-branched  roots  reached  a  distance 
of  16  to  18  inches  on  all  sides  of  the  plant,  the  longest  ones  often  lying  in  the 
surface  inch  or  two  of  mellow  soil  (fig.  28).  The  deeper  roots,  which  ran 


Fig.  28. — Bouteloua  hirsuta  from  Phillipsburg,  on  July  1 
of  second  year  after  planting. 


64 


EXPERIMENTS  DURING  1921. 


obliquely  downward,  extended  to  depths  of  12  and  a  few  to  24  inches.  Many 
new  thick,  wrhite  roots  only  2  to  4  inches  long  came  off  from  the  new  tillers. 
Bouteloua  gracilis  had  well-developed  clumps  4  to  7  inches  high.  The  fine 
fibrous  root  system  was  very  similar  to  that  of  the  preceding,  especially  in 
the  number  and  extent  of  fine  lateral  branches.  However,  it  differed  in 
having  a  smaller  lateral  spread  (about  12  inches)  and  greater  depth  of  pene¬ 
tration.  Many  of  the  roots  reached  2  and  some  nearly  3  feet  in  depth. 

Andropogon  scoparius  produced  densely  rooted  plants  8  to  12  inches  tall 
and  so  wTell  tillered  that  they  formed  a  continuous  sod.  The  dense  network 
of  roots  and  branches  reached  a  working  level  of  30  inches  and  a  maximum 


29  30  31 


Fig.  29. — Andropogon  scoparius  from  Phillipsburg,  on  July  1  of  second  year  after  planting. 

Fig.  30. — Roots  of  Andropogon  nutans  after  the  block  of  sod  had  been  transplanted  for  2.5  months 
at  Burlington. 

Fig.  31. — Roots  of  Elymus  canadensis  at  end  of  June  of  second  year  after  the  block  of  sod  had  been 
transplanted  and  watered  at  Burlington. 

depth  of  37  inches.  Many  new  roots  of  the  current  season’s  growth  were  only 
6  to  12  inches  long.  The  last  3  to  8  inches  of  these,  as  well  as  those  of  many 
of  the  rapidly  growing  ones  of  1920,  were  1  to  1.5  mm.  thick,  glistening  white, 
and  destitute  of  branches  (fig.  29).  Stipa  viridula  was  represented  by  bunches 
4  to  9  inches  in  height.  The  roots  were  abundant  to  a  depth  of  2  feet,  some 
extending  to  the  4-foot  level.  They  had  a  lateral  spread  of  12  to  14  inches 
on  all  sides  of  the  plant.  These  data  are  sufficient  to  show  the  fairly  deep 
root  penetration  of  the  species  by  midsummer  of  the  second  year  in  denuded 
quadrats.  It  also  explains  how  they  persist  so  tenaciously  during  periods  of 
drought  after  they  have  had  a  year’s  growth. 

The  removal  of  the  preceding  species  left  Andropogon  nutans  alone  in  the 
1920  quadrats.  It  grew  very  well,  reaching  a  height  of  15  to  18  inches  by  fall 
and  producing  a  few  flower-stalks  40  inches  tall.  During  1922  it  made  ex- 


SEEDLING  TRANSPLANTS. 


65 


cellent  growth  but  did  not  blossom,  while  in  1923  it  reached  a  height  of  2 
feet  and  flowered  abundantly. 

Seedling  Transplants. 

Seedlings  of  13  species  were  transplanted  into  high  prairie  on  May  11, 
when  3  or  4  weeks  old  (table  61).  As  at  all  stations,  these  seedlings  were 
thoroughly  watered  when  planted  and  during  a  period  of  10  days  thereafter 
whenever  necessary.  Notwithstanding  this  care,  two  weeks  later  two  of  the 
four  lots  of  Andropogon  nutans ,  Aristida  purpurea,  Bouteloua  racemosa,  and 
Koeleria  cristata  had  died.  Agropyrum  glaucum,  Elymus  canadensis,  Stipa 
comata,  and  S.  viridula  were  eaten  back  by  grasshoppers  and  many  individuals 
had  died.  One  lot  of  Bouteloua  gracilis  had  also  died,  and  Andropogon  fur - 
catus,  Stipa  spartea,  and  Liatris  punctata  were  the  only  ones  which  had  not 
suffered  a  high  mortality.  The  soil  at  this  station  is  of  such  a  type  that  it 
becomes  quite  compact  following  heavy  rains  or  watering.  This  is  detri¬ 
mental  to  seedlings,  as  well  as  germinating  seeds,  since  the  surface  crust 
hinders  aeration  and  offers  more  or  less  of  a  mechanical  barrier  to  tender 
growing  parts.  When  dry  it  cracks  and  in  this  way  injures  the  plants  by 
mechanical  tearing  of  roots,  rhizomes,  etc.,  near  the  surface.  At  Phillips- 
burg  and  Burlington  the  soil  is  of  such  texture  that  it  is  mellow  at  all  times. 
However,  all  species  were  represented  until  the  middle  of  June,  after  which 
Stipa  comata  and  S.  viridula  died,  and  Agropyrum,  Aristida,  Elymus,  and 
Liatris  also  succumbed  during  July.  The  other  7  species  came  through  the 
season  in  fair  to  excellent  condition,  although  much  reduced  in  number. 
Bouteloua  hirsuta  flowered. 

A  similar  lot  of  seedlings  of  the  same  age  was  transplanted  at  Phillipsburg 
on  May  19.  These  were  in  groups  varying  from  2  to  6  per  species  (table  62). 
By  June  9  all  were  flourishing  and  most  of  them  continued  to  do  so  throughout 
the  month.  By  July  25,  Agropyrum,  Elymus,  and  Stipa  spartea  had  suffered 
heavy  losses;  Koeleria,  Stipa  comata,  and  S.  viridula  were  nearly  all  dead, 
and  by  the  end  of  the  summer  they  had  disappeared.  Agropyrum,  Andro¬ 
pogon  furcatus,  Bouteloua  gracilis,  Elymus,  and  Liatris  scariosa  were  nearly 
all  dead  or  dying,  the  last  having  been  eaten  to  the  ground.  However,  A. 
nutans,  B.  hirsuta,  Liatris  punctata,  and  Stipa  spartea  were  in  fair  to  excellent 
condition. 

Seedlings  were  transplanted  at  Burlington  on  May  20  (table  63).  By  June 
10,  Koeleria  had  died,  while  Agropyrum,  Liatris  scariosa,  and  Stipa  viridula 
had  suffered  a  high  mortality.  However,  the  other  species  were  in  fairly 
good  condition.  By  the  end  of  the  month,  Liatris  scariosa  and  Stipa  viridula 
had  succumbed  and  most  of  the  other  species  had  lost  heavily.  Many  had 
their  leaves  rolled  or  were  badly  wilted.  By  the  end  of  July,  A.  nutans,  B. 
hirsuta,  and  B.  gracilis  alone  were  barely  alive  and  these  died  during  August. 

Summary. 

The  sequence  of  germination  was  the  same  as  in  preceding  years  (table 
24),  i.  e.,  Lincoln  being  highest  (81  per  cent),  Phillipsburg  second  (68  per 
cent),  and  Burlington  last  (43  per  cent).  On  the  basis  of  establishment, 
however,  Phillipsburg,  unlike  the  preceding  year,  ranked  first  with  60  per 
cent,  Lincoln  second  (40  per  cent),  and  Burlington  third  (7  per  cent)  The 


66 


EXPERIMENTS  DURING  1921. 


unusually  favorable  rainfall  at  Phillipsburg  during  spring  and  early  summer 
has  already  been  pointed  out,  as  well  as  the  relatively  favorable  light  con¬ 
ditions  for  surface-sown  plants  (p.  60)  . 

On  the  basis  of  survival  of  seedlings,  Phillipsburg  also  ranked  first,  none 
surviving  at  Burlington.  As  to  the  surface-sown  plants  of  1920,  none  were 
left  at  either  Lincoln  or  Phillipsburg  for  growth  during  1921,  but  Stipa 


Table  24. — Summary  of  planting  experiments  at  the  three  stations,  1921. 


Method  of 
planting. 

P.  ct.  of  species  germinating. 

P.  ct.  of  germination  established. 

Lincoln. 

Phillips¬ 

burg. 

Burling¬ 

ton. 

Lincoln. 

Phillips¬ 

burg. 

Burling¬ 

ton. 

Surface  sowing . 

79 

100 

38 

9 

83 

0 

Trench . 

92 

43 

15 

45 

50 

0 

Denuded  quadrat. . . . 

71 

61 

76 

65 

63 

21 

Average . 

81 

68 

43 

40 

65 

7 

Seedlings . 

54 

75 

0 

viridula  survived  at  Burlington.  Among  the  5  survivors  of  the  1920  trench 
planting  at  Lincoln,  none  died  during  1921;  1  was  winterkilled  in  1921-22, 
but  the  others  were  growing  fairly  well  at  the  end  of  the  summer  of  1923. 
At  Phillipsburg  only  2  of  the  6  species  planted  lived,  but  both  of  these  grew 
well,  flowered  from  time  to  time,  and  persisted  to  the  end  of  1923.  None 
survived  the  1920  summer  at  Burlington.  Among  the  8  survivors  in  the 
1920  quadrats  at  Lincoln,  all  lived  throughout  the  next  summer,  but  2  were 
winterkilled.  The  6  remaining  species  did  well  until  the  fall  of  1923.  At 
Phillipsburg  all  but  1  were  excavated  for  root  study.  This  plant  made  an 
excellent  growth  and  flowered  from  time  to  time  until  the  end  of  1923.  The 
3  species  at  Burlington  lived  not  only  through  the  1921  season,  but  also  during 
1922  and  1923,  all  but  Stipa  viridula  coming  into  blossom. 

Sod  Transplants. 

Between  March  20  and  31,  sods  of  16  species  were  planted  on  high  prairie 
(table  64).  Distichlis  was  secured  from  the  salt-flats,  Bulbilis  from  overgrazed 
low  prairie,  Bouteloua  gracilis  and  B.  kirsuta  from  gravel-knoll,  Andropogon 
furcatus,  A.  nutans ,  Panicum  virgalum,  and  Poa  pralensis  from  low  prairie, 
and  Spartina  cynosuroides  from  the  swamp.  The  rest  were  high-prairie 
species.  All  made  a  good  growth  during  the  summer,  except  Distichlis,  which 
was  nearly  all  dead  by  August  31,  and  all  blossomed  except  the  three  Andro- 
pogons ,  Bouteloua  kirsuta,  B.  gracilis,  Koeleria,  and  Spartina.  During  1922 
all  not  only  survived,  but  Bulbilis,  Panicum,  and  Spartina  increased  their 
area.  However,  by  the  end  of  August,  Agropyrum,  Distichlis,  and  Elymus 
were  doing  very  poorly,  owing  in  part  to  the  severe  drought.  Twelve  of  the 
16  species  blossomed  (table  64).  Koeleria  died  during  the  following  winter. 
The  rest  survived  the  following  summer,  but  by  August  Bouteloua  gracilis, 
Agropyrum,  Distichlis,  and  both  lots  of  Elymus  were  in  straits.  Bulbilis, 
Stipa,  and  Panicum  alone  produced  flower-stalks  before  the  final  check  was 


SOD  TRANSPLANTS. 


67 


made  in  August.  This  lack  of  vigor  was  probably  a  result  of  the  extremely 
dry  late  summer,  fall,  and  winter  preceding  (p.  109).  The  1920  sods 
made  fair  to  good  growth,  except  for  one  block  of  Andropogon  furcatus 
and  two  of  Distichlis,  which  were  nearly  dead  by  the  last  of  August.  The 
following  did  not  blossom:  Agropyrum ,  A.  furcatus,  Bouteloua  gracilis,  B. 
racemosa,  Distichlis,  Spdrtina,  and  Stipa.  During  1922  a  severe  drought 
occurred  in  late  summer  and  both  plantings  of  Distichlis  and  Elymus  and  one 
of  Koeleria  succumbed.  Agropryum,  one  Andropogon  scoparius,  and  Poa 
pratensis  were  in  very  poor  condition  at  the  end  of  the  summer,  while  Andro¬ 
pogon  nutans,  A.  scoparius ,  Poa,  and  Stipa  alone  had  seeded.  The  following 
winter  one  Stipa  died,  but  all  of  the  others  made  a  fair  to  good  growth  during 
this  fourth  summer.  On  August  25  only  the  following  had  blossomed  or 
showed  signs  of  developing  flower-stalks:  Poa,  Bouteloua  gracilis,  B.  racemosa, 
Koeleria,  and  Panicum. 

Sods  of  the  same  species  as  those  used  at  Lincoln  during  1921,  except 
Bouteloua  gracilis,  Bulbilis,  Distichlis,  and  Spartina,  were  secured  from  the 
various  stations  at  Lincoln  and  transplanted  into  the  short-grass  sod  at  Bur¬ 
lington  on  April  15.  As  in  1920,  they  were  placed  in  duplicate  rows,  one 
being  thoroughly  watered  5  times  during  the  season  (table  65).  By  May 
20  the  effects  of  drought  were  apparent.  The  leaves  on  many  species  were 
rolled  and  the  leaf-tips  dead.  Others  had  been  frayed  by  whipping  in  the 
wind,  a  very  common  phenomenon  in  this  region  among  both  native  and 
crop  plants.  Koeleria  and  Stipa  were  almost  dead.  The  plants  in  the 
watered  row  were  in  better  condition. 

On  June  29,  the  root  development  was  examined  in  two  species,  which  had 
been  growing  for  a  period  of  75  days.  Andropogon  nutans  was  in  fairly  good 
shape  and  had  made  a  growth  of  4  to  6  inches.  The  block  of  sod  was  found 
to  be  in  close  contact  with  the  soil  on  all  sides.  The  old  roots  had  practically 
all  died,  though  in  a  few  instances  laterals  from  them  had  continued  growth. 
Many  new  white  roots  had  originated  from  the  rhizomes  and  ended  at  6  to  12 
inches  depth.  They  were  evidently  growing  rapidly,  since  3  to  6  inches  of  the 
tips  were  unbranched;  nearer  their  origin  they  were  thickly  beset  with  short 
branches.  Several  longer  roots  penetrated  from  18  to  32  inches,  but  none 
spread  much  laterally,  and  all  were  well  branched  (fig.  30).  The  soil  was 
moister  under  the  block  of  sod  than  elsewhere  to  a  depth  of  20  inches.  Panicum 
virgatum  was  growing  nicely  and  had  reached  a  height  of  10  inches.  As 
before,  the  old  roots  were  nearly  all  dead,  but  many  new  ones  descended 
vertically  and  were  fairly  abundant  to  24  to  30  inches.  At  the  last  depth  they 
came  in  contact  with  the  dry  hard-pan.  They  were  densely  beset  with 
laterals  to  near  the  tip. 

By  June  29,  Stipa  had  died  in  the  unwatered  row  and  Elymus  and  Koeleria 
were  nearly  dead.  Even  some  of  the  species  in  the  watered  row  were  doing 
poorly,  especially  Poa  and  the  three  andropogons.  By  late  July  Andropogon 
nutans  and  Poa  had  died  in  the  watered  row  and  several  other  species  were  in 
bad  condition.  In  the  unwatered  row,  Elymus  and  Poa  had  succumbed, while 
Andropogon  furcatus,  Bouteloua  hirsuta,  and  Koeleria  died  soon  after.  Autumn 
found  only  7  of  the  11  species  alive  in  the  watered  row,  and  these  were  repre¬ 
sented  by  mere  remnants  of  the  original  fine  blocks  of  sod.  Of  the  survivors, 
Agropyrum,  A.  scoparius,  Bouteloua  hirsuta,  Elymus,  and  Stipa  were  high- 


68 


EXPERIMENTS  DURING  1921. 


prairie  species,  and  A.  furcatus  was  from  the  lowland.  Agropyrum  alone  had 
blossomed.  Of  the  11  duplicate  unwatered  species  (2  having  been  dug  up) 
only  Agropyrum,  Bouteloua  racemosa,  and  Andropogon  scoparius  remained, 
and  Agropyrum  alone  had  a  single  flower-stalk. 

During  1922,  both  Agropyrum  and  Bouteloua  racemosa  in  the  unwatered  row 
survived,  although  both  suffered  severely  from  drought,  and  Andropogon 
scoparius  was  winterkilled.  Agropyrum  put  forth  flower-stalks  mostly  less 
than  a  foot  high,  and  the  spikes  were  very  much  dwarfed.  In  the  lot  that 
were  formerly  watered,  Andropogon  scoparius  died  in  July.  The  other  6 
species  made  a  fair  to  good  growth,  often  showing  the  effects  of  drought  in 
the  rolled  leaves  or  dead  leaf-tips,  as  well  as  by  the  dwarfing  of  the  whole 
plant.  Bouteloua  racemosa,  B.  hirsuta,  Agropyrum,  and  Elymus  alone  blos¬ 
somed.  Andropogon  furcatus,  Bouteloua  hirsuta,  and  Bouteloua  racemosa  died 
before  the  next  spring.  The  single  survivor  of  the  unwatered  lot,  Agropyrum, 
reached  a  height  of  only  11  inches  the  following  summer,  and  did  not  blossom 
or  extend  its  territory  into  the  surrounding  short-grasses.  Agropyrum  in  the 
other  lot  grew  only  slightly  better,  Elymus  was  represented  by  only  2  shoots, 
and  Stipa  by  a  small  c'ump,  while  Bouteloua  racemosa  alone  made  a  good 
growth  and  seeded.  Although  the  season  was  unusually  favorable  for  growth, 
the  results  indicate  that  one  more  year  would  probably  have  been  sufficient  to 
eliminate  most  if  not  all  of  the  transplants.  As  to  the  growth  of  the  1920 
transplants  at  this  station,  it  may  be  recalled  that  none  died  during  the  first 
season,  even  in  the  unwatered  row,  but  all  suffered  from  drought  and  were 
dwarfed.  During  1921  none  were  watered. 

Root  Development. 

On  June  28-29  the  root  development  of  several  species  was  examined. 
Elymus,  which  had  blossomed  the  preceding  season,  had  made  a  fair  growth 
in  the  unwatered  row,  reaching  a  height  of  21  inches  with  flower-stalks  appear¬ 
ing.  The  old  roots  had  not  renewed  their  growth,  but  laterals  on  them  were 
functioning  (fig.  31),  and  in  one  case  a  large  lateral  had  replaced  the  cut  main 
root.  It  was  traced  to  a  depth  of  20  inches.  Many  new  roots  reached  a 
depth  of  18  inches,  while  a  few  penetrated  to  the  hard-pan,  about  30  inches 
deep.  All  were  quite  profusely  branched  to  near  the  tips,  and  the  lateral 
spread  was  about  12  inches.  Some  new  roots,  evidently  of  the  current  year’s 
growth,  extended  just  through  the  old  block  of  sod. 

Andropogon  furcatus  was  excavated  in  the  unwatered  row.  The  original 
sod,  which  was  in  complete  contact  with  the  soil,  was  a  foot  square  and  8 
inches  deep.  The  new  growth  of  leaves  was  about  8  inches  high.  Most  of 
the  old  roots  had  died,  but  new  ones  had  grown  out  thickly  from  the  rhizomes. 
Many  of  these  penetrated  to  the  hard-pan  layer  at  28  to  30  inches,  but  only 
slightly  into  it.  All  of  the  roots  were  well  branched,  but  were  very  dry,  like 
the  soil  in  which  they  grew.  The  dry,  mellow  loess  below  the  hard-pan  layer 
(which  was  8  to  12  inches  thick)  contained  roots  of  the  short-grasses  and 
Psoralea.  There  was  very  little  lateral  spread  of  the  roots  beyond  the  area 
occupied  by  the  original  block  of  sod. 

Koeleria,  Stipa  spartea,  and  Panicum  virgatum  were  excavated  in  the 
watered  row,  which  had  also  received  some  run-off  water  because  of  its  loca¬ 
tion  near  a  furrow  separating  an  adjoining  plowed  area.  The  clump  of 


SOD  TRANSPLANTS. 


69 


Koeleria  was  3.5  inches  in  diameter  and  had  flower-stalks  12  inches  tall,  with 
rather  normal  spike  development  at  a  height  of  6  to  15  inches.  The  roots, 
although  very  fine,  were  easily  distinguished  from  those  of  the  short-grasses 
by  their  yellowish  color  and  slightly  larger  size.  A  great  mass  of  profusely 
branched  roots  filled  the  soil  to  a  depth  of  about  18  inches,  a  few  penetrating 
8  inches  deeper.  A  lateral  spread  of  14  inches 
in  the  surface  inch  of  soil  was  determined,  the 
occupation  of  a  considerable  area  on  all  sides 
of  the  plant  being  characteristic  of  the  species. 

Stipa  spartea  had  made  a  growth  of  2  feet, 
with  5  flower-stalks,  some  of  which  were  34 
inches  tall,  and  formed  a  representative  clump. 

The  roots  reached  a  maximum  depth  of  34 
inches  in  the  fairly  moist  soil,  many  ending  at 
or  above  2  feet.  The  lateral  spread  was  about 
normal  (10  inches),  but  the  roots  as  a  whole 
were  more  profusely  branched  than  is  usual  in 
its  native  region.  Panicum  virgatum,  which 
flowered  the  preceding  season,  had  made  a  good 
growth,  reaching  a  height  of  18  inches.  The 
root  development  was  remarkable.  The  coarse 
roots,  2  to  4  mm.  in  diameter,  pursued  a  nearly 
vertically  downward  course  to  a  maximum 
depth  of  7.3  feet,  spreading  only  a  little  near 
the  surface.  The  profound  branching  to  the 
extreme  depth  of  penetration  is  shown  in  figure 
32.  Branches  at  the  rate  of  25  per  inch  were 
not  uncommon,  and  many  of  the  roots  were 
branched  to  their  tips.  In  fact,  the  profuse 
branching,  which  undoubtedly  was  a  response 
to  the  dry  soil,  can  scarcely  be  overemphasized. 

It  stood  out  in  marked  contrast  to  the  rather 
poorly  developed  lateral  roots  found  on  plants 
growing  in  lowland  soil  near  Lincoln  (Weaver, 

1919:4). 

Notwithstanding  the  root  growth  of  these 
transplants,  the  severe  drought  conditions 
caused  the  death  of  several  species.  One  sod 
of  the  watered  Koeleria  and  one  in  the  un¬ 
watered  row  succumbed.  In  the  unwatered 
row,  1  Andropogon  scoparius  was  winter-killed, 

2  individuals  of  Elymus ,  and  all  3  of  Poa 
died.  Agropyrum  was  the  only  species  that 
increased  its  territory  perceptibly.  It  invaded 
the  short-grass  sod  on  all  sides  for  a  distance  of  about  18  inches,  the 
new  shoots  from  the  rhizomes  reaching  a  height  of  8  to  13  inches.  How¬ 
ever,  none  of  these  or  those  of  the  original  block  bore  flower-stalks. 
Bouteloua  racemosa,  Elymus ,  Stipa,  and  Panicum  (in  the  watered  row  only) 
bore  a  few  flower-stalks  and  seeded,  as  did  also  Poa  and  Koeleria ,  the 


Fig.  32. — Roots  of  Panicum  vir¬ 
gatum  at  end  of  June  of  second 
year  after  the  block  of  sod  had 
been  transplanted  and  watered 
at  Burlington. 


70 


EXPERIMENTS  DURING  1921. 


last  in  the  unwatered  row  also.  All  suffered  severely  from  spring  and  summer 
drought,  and  in  general  growth  was  poor.  Most  of  the  species,  including  such 
late  bloomers  as  A.  scoparius,  A.  furcalus ,  and  Panicum,  took  on  their  late 
autumn  reddish  color,  dried  out,  and  went  into  winter  condition  by  August  1. 
As  a  whole,  those  that  had  not  been  watered  the  preceding  season,  and  hence 
were  less  well  established,  suffered  most.  During  1922  none  of  the  plants 
died  in  the  lot  which  had  been  watered,  but  Koeleria  of  the  unwatered 
lot  succumbed  in  July.  Of  the  former,  Agropyrum  had  extended  its  area  3 
or  more  feet  on  all  sides,  even  into  the  densest  sod.  Although  it  flowered 
profusely  in  its  original  area  at  a  height  of  about  2  feet,  only  a  few  dwarfed 
flower-stalks  appeared  in  the  invaded  area.  This  was  the  only  species  which 
extended  its  area,  though,  on  the  other  hand,  the  short-grasses  were  unable  to 
invade  markedly.  Because  of  the  severe  drought  of  July  and  August,  the 
grasses  at  this  time  mostly  took  on  their  late  autumn  or  winter  color  and 
habit.  Aside  from  Agropyrum ,  Stipa,  Elymus,  Koeleria,  and  Bouteloua  race- 
mosa  blossomed ;  the  last,  unlike  the  others,  had  flower-stalks  and  inflorescences 
of  about  normal  size.  In  the  row  that  was  not  watered  the  preceding  year, 
conditions  were  much  more  severe.  Agropyrum  possessed  only  a  few  flower- 
stalks,  while  Panicum  put  forth  a  few  small  panicles  at  8  inches  height. 
Elymus  and  Koeleria  also  blossomed. 

The  very  dry  fall  and  winter  following  took  severe  toll.  Of  the  15  lots  of 
plants  in  the  area  formerly  watered,  4  died,  while  among  those  less  well 
established  8  succumbed,  leaving  Agropyrum  as  the  sole  survivor.  Notwith¬ 
standing  the  excellent  growing  conditions  of  the  following  summer  (1923),  it 
had  no  flower-stalks,  but  had  sent  out  a  few  rhizomes  to  distances  of  2  to  3 
feet.  The  rest  of  the  plants  received  extra  water  from  a  furrow  which  was 
only  2  feet  distant  and  separated  the  unbroken  and  broken  land.  Hence, 
their  growth  was  very  good.  Agropyrum  had  spread  nearly  4  feet,  but 
no  flower-stalks  occurred  in  this  sodded  area.  Elymus  had  also  extended 
its  area  over  a  foot,  but  another  block  of  the  same  species  died.  Panicum , 
Bouteloua  racemosa,  and  Stipa  blossomed.  Among  the  forms  introduced  with 
the  sods,  Erigeron  ramosus  blossomed  the  second  year  (1921),  as  did  also 
Sporobolus  asper,  though  both  died  later.  Brauneria  pallida  in  one  instance 
made  a  good  vegetative  development  only,  while  in  another  case  it  blossomed 
normally  the  second  year  after  transplanting  before  succumbing.  Aster 
multi flor us  occurred  in  several  blocks  of  sod  and  usually  spread  a  foot  or  more 
by  rhizomes;  it  blossomed  profusely.  In  some  cases  it  persisted  4  years 
near  the  furrow,  but  in  others  it  soon  succumbed. 

EXPERIMENTS  AT  OTHER  STATIONS,  1921. 

Physical  Factors. 

Rainfall  and  Holard. 

Studies  on  experimental  vegetation  were  continued  in  the  series  of  edaphic 
stations  at  Lincoln,  at  Nebraska  City,  and  Colorado  Springs  during  1921. 
The  general  conditions  of  precipitation  at  Lincoln  have  already  been  given 
(p.  56).  The  season  at  Nebraska  City  was  one  of  drought.  The  precipitation 
from  February  to  July  was  decidedly  below  normal,  that  of  April,  May,  and 
June  being  0.86,  1.56,  and  0.52  inches  respectively  below  the  mean.  However, 


EDAPHIC  STATIONS. 


71 


July  had  an  excess  of  5.17  inches,  but  August  was  slightly  below  normal. 
No  efficient  rain  fell  between  May  9  and  26  or  from  June  18  to  July  2.  The 
holard  at  the  Nebraska  City,  low-prairie,  and  gravel-knoll  stations  is  given 
in  table  25.  Notwithstanding  the  decreased  rainfall,  the  soil  at  Nebraska 
City  usually  had  a  margin  of  10  per  cent  above  the  hygroscopic  coefficient. 
In  fact,  a  more  constant  supply  was  maintained  here  than  on  the  low  prairie 
at  Lincoln,  where  the  chresard  in  the  surface  6  inches  was  practically  exhausted 
during  the  last  half  of  June.  An  abundant  supply  was  at  all  times  available 
below  the  6-inch  level.  Even  on  the  gravel-knoll  conditions  were  quite 
favorable  as  compared  with  the  preceding  year.  However,  the  xerophytism 
of  this  habitat  is  shown  by  the  small  chresard,  usually  only  1  to  6  per  cent, 
even  at  depths  of  3  or  4  feet. 

Evaporation  and  Temperature. 

The  average  daily  evaporation  at  Nebraska  City  (fig.  33)  was  considerably 
lower  (often  33  per  cent)  than  on  the  high  prairie.  In  general,  evaporation 
on  the  gravel-knoll  was  greater  than  on  high  prairie.  This  was  especially 
true  during  the  earlier  and  later  parts  of  the  season.  The  average  daily 
air-temperature  at  Nebraska  City  was  usually  higher  than  that  at  Lin¬ 
coln,  and  during  the  first  3  weeks  of  June  it  ranged  from  2°  to  11°  F.  higher. 
This  was  largely  due  to  the  much  higher  average  night  temperatures  (often 
6°  to  10°  F.),  since  the  day  temperatures  nearly  always  averaged  lower  than 
those  at  Lincoln.  The  temperature  of  the  soil  at  18  inches  was  constantly 
1°  to  3°  warmer. 


Fig.  33. — Average  daily  evaporation  on  high  prairie  (solid  line),  gravel-knoll, 
Lincoln  (short  broken  lines),  and  at  Nebraska  City  (long  broken  lines),  1921. 


Planting  Results. 

Surface  Sowing. 

During  1921,  surface  sowings  were  made  on  the  low  prairie  at  Lincoln  and 
at  Nebraska  City.  Of  the  9  species  planted  at  Lincoln  on  April  23,  Aristida 
purpurea  and  Bouteloua  gracilis  did  not  germinate.  Elymus  canadensis  had 
died  by  June  27,  as  the  following  did  also  during  July  and  August:  Lespedeza 
capitata ,  Liatris  punctata ,  L.  scariosa,  Sporobolus  asper,  and  Stipa  viridula. 
Koeleria  cristata  was  still  alive  in  September,  but  was  missing  the  following 


72 


EXPERIMENTS  DURING  1921. 


May.  Owing  to  the  low  light  intensities,  all  of  the  seedlings  were  extremely 
attenuated  as  compared  with  those  growing  in  the  quadrats,  and  were  unable 
to  make  any  real  growth.  The  ability  of  Koeleria  to  endure  shading  was  noted 


Table  25. — Holard  in  excess  of  the  hygroscopic  coefficient  at  Nebraska 
City ,  Lincoln  low  prairie ,  and  gravel-knoll ,  1921. 

Nebraska  City. 


Date. 

0  to  0.5 
foot. 

0.5  to  1 
foot. 

1  to  2 
feet. 

2  to  3 
*  feet. 

3  to  4 
feet. 

Apr.  9 . 

24.4 

21.4 

18.5 

11.7 

8.7 

Apr.  23 . 

19.4 

20.1 

•  •  •  • 

•  •  •  • 

•  •  •  • 

May  6 . 

10.7 

16.5 

15.6 

.... 

,  ,  ,  , 

May  20 . 

10.1 

16.1 

16.8 

12.6 

12.8 

June  3 . 

23.8 

21.6 

19.5 

.... 

.... 

June  24 . 

12.0 

9.9 

15.0 

13.6 

13.8 

July  15 . 

9.2 

14.9 

14.3 

11.5 

9.6 

Aug.  13 . 

14.8 

10.5 

16.0 

15.9 

10.1 

Aug.  26 . 

12.8 

10.2 

10.9 

12.5 

9.1 

Hygro.  coeff . 

12.1 

11.7 

12.3 

13.7 

12.9 

Low  Prairie. 

Apr.  9 . 

20.8 

25.2 

Apr.  23 . 

28.4 

23.3 

21.5 

20.5 

29.7 

May  18 . 

10.5 

24.8 

21.6 

22.3 

23.0 

May  25 . 

9.7 

20.0 

.... 

.... 

•  •  •  • 

June  1 . 

6.8 

16.4 

.... 

•  •  •  • 

.... 

June  7 . 

9.7 

21.7 

21.3 

23.9 

22.4 

June  22 . 

1.4 

16.0 

19.2 

.... 

.... 

June  29 . 

0.3 

11.1 

14.2 

16.8 

.... 

July  20 . 

25.4 

23.0 

15.3 

15.2 

18.9 

July  28 . 

18.2 

17.9 

.... 

•  •  •  • 

.  .  .  . 

Aug.  3 . 

15.0 

12.1 

14.5 

.... 

.... 

Aug.  23 . 

12.3 

14.9 

11.8 

13.7 

19.3 

Hygro.  coeff . 

11.8 

11.1 

10.3 

10.2 

11.9 

Gravel-Knoll. 

Apr.  9 . 

6.5 

3.9 

5.0 

5.0 

1.0 

May  18 . 

6.3 

5.3 

6.6 

9.2 

1.7 

May  25 . 

0.1 

-0.2 

•  •  •  • 

•  •  •  • 

.... 

June  1 . 

3.3 

-0.3 

.... 

.... 

.... 

June  7 . 

7.8 

6.4 

11.8 

5.7 

1.2 

June  22 . 

-0.1 

0.4 

3.4 

4.5 

3.9 

June  29 . 

1.9 

3.3 

3.1 

3.3 

.... 

July  13 . 

4.5 

2.6 

3.7 

•  •  .  . 

.... 

July  20 . 

4.8 

3.1 

2.1 

4.7 

9.6 

July  28 . 

0.4 

1.3 

•  •  .  • 

.... 

.... 

Aug.  3 . 

4.8 

4.0 

2.7 

.... 

.... 

Aug.  10 . 

3.1 

2.3 

2.0 

6.7 

10.8 

Hygro.  coeff . 

5.2 

4.9 

3.1 

2.8 

7.4 

in  many  instances,  this  adaptation  probably  resulting  from  its  smaller  stature. 
Light  values  at  the  soil-surface  in  the  several  stations  are  summarized  in 
table  26. 


EDAPHIC  STATIONS*.  LIGHT  VALUES. 


73 


Table  26. — Light  values  at  the  several  stations. 


Cover. 


High  prairie,  Lincoln. 

May  28,  1922  :* 

Andropogon  scoparius . 

Psoralea  tenuiflora  floribunda 
Psoralea,  Kuhnia  glutinosa. . 

Brauneria  pallida . 

Astragalus  crassicarpus . 

July  25,  1921: 

Mixed  grasses . 

Average  density . 

Light  cover . 

Medium,  4  inches  above 

surface . 

Light . 

Trench,  medium  cover . 


Swamp,  Lincoln. 

May  28,  1922: 

Spartina  cynosuroides . 
Phalaris  arundinacea .  . 
Mixed  grasses,  etc .... 
Mixed  grasses,  average . 
August  24,  1922: 

Spartina  cynosuroides 

Densest  places . 

Medium  density .... 
Most  open . 


Nebraska  City. 

June  3,  1921 :3 

Stipa  spartea . 

Andropogon  furcatus . 

Andropogon  scoparius . 

Liatris  scariosa . 

Grasses,  Amorpha  canescens. 

Rosa  arkansana . . 

Brauneria  pallida . . 

A.  scoparius,  Koeleria  cristata 

A.  scoparius,  A.  nutans . . 

Stipa  spartea . 

Very  open  grass  mixture . 

Ceanothus  ovatus . 

A.  furcatus  at  side  of  quadrat. 
June  3,  1922: 

Very  open  grass  mixture . 

Euphorbia  corollata,  grasses. . 

Rosa  arkansana . 

Baptisia  bracteata . 

Vernonia  fasciculata . 

A.  furcatus,  Desmodium . 

Stipa  spartea,  Andropogon.  .  . 
Koeleria  cristata,  Poa  praten- 

sis . 

Ceanothus  ovatus . 


Per  cent. 


15 

20  to  26 
6 

10  to  15 
2.5  to  3.5 

8.3 

5.0 

9.5 

15.0 
17.0 
20  to  23 


7.5 

6.5 
4.5  to  20 

11.2 


1.5  to  2 . 6 
4  to  5.7 
11.4  to  16.6 


18 
11.5 
17.5  to  26.5 

7.5 
8  to  11.5 

2.5 
7 

15 

20 

8  to  10 
60 

1.5 
15 

40  to  45 
20 

6.5 
6.5 

.  8 
9 
9 

22  to  26 
2  to  2 . 5 


Cover. 


Low  prairie,  Lincoln. 

May  28,  1922: 

Mixed  grasses: 

Above  1921  growth . 

Average . 

Under  old  growth . 

June  14,  1922 :2 

Surface  seeding,  average  den¬ 
sity . 

Side  of  1922  trench: 

Spartina  cynosuroides . 

Verbena  stricta . 

Light,  mixed . 

Andropogon  furcatus . . 

Grasses,  Art.  ludoviciana. .  . 

Lighter  mixed  cover . 

South  edge  of  1922  quadrats.  .  . 
West  edge  of  1922  quadrats. . .  . 
July  25,  1922: 

Mixed  grasses: 

Average  density . 

Lighter . 

Very  dense . 

4  inches  above  trench  surface : 

Medium . 

Lighter . 

Dense . 


Phillipsburg. 

June  10,  1922: 

Bouteloua  gracilis  and  Bul- 

bilis  dactyloides . 

Psoralea  tenuiflora . 

Elymus  canadensis . 

Andropogon  furcatus . 

A.  scoparius . 

Bouteloua,  Gaura,  Lygodes- 

mia . 

Verbena  stricta . 

Grasses: 

Edge  of  1922  trench . 

Edge  of  1921  quadrat.  .  .  . 


Burlington. 

June  11,  1922: 

Bulbilis  dactyloides4 . 

Bulbilis,  B.  gracilis,  open4. 

Bulbilis,  very  dense4 . . 

Agropyrum  glaucum6 

Stipa  spartea . 

Short-grasses : 

Malvastrum  coccineum4 . 
Erysimum  asperum4 

Edge  of  1922  trench . 

Edge  of  1920  quadrat . 

Edge  of  1922  quadrat . 


Per  cent. 


7 . 5  to  28 
16 

3.4  to  14 


5  to  7 

12.5 

5 

12 

7  to  12 

8  to  13 

26 

15  to  27 
10 


2.5  to  4 
12 

1.5 

11 

16 

4.5 


60  to  80 
35 
24 

3  to  8 

4  to  5 

10 

11.5 


30 

to 

33 

20 

to 

26 

45 

to 

50 

71 

to 

83 

25 

20 

to 

43 

15 

43 

26 

56 

20 

37.5 

to 

45 

1  Burned  over  in  late  winter. 

2  This  portion  of  the  area  burned  over  in  late  winter. 

3  Mowed  the  preceding  September. 


4  Photometer  sunken  so  as  to  be 
level  with  soil  surface. 

6  Transplanted  sods. 


74 


EXPERIMENTS  DURING  1921. 


Of  the  9  species  sown  on  the  surface  at  Nebraska  City,  Liatris  scariosa 
and  Pinus  ponder osa  failed  to  germinate,  squirrels  having  eaten  the  seeds 
of  the  latter.  A  single  plant  of  Elymus  was  found,  but  it  died  before  June. 
By  June  24,  Liatris  punctata  and  Bromus  inermis  were  also  dead,  the  latter 
having  been  eaten  to  the  ground  by  grasshoppers.  Sporobolus  asper  and 
Stipa  viridula  (also  somewhat  eaten)  died  in  later  summer.  Bouteloua  gracilis 
and  B.  hirsuta  survived  the  season,  reaching  a  height  of  1  or  2  inches,  tiller¬ 
ing  somewhat,  but  persisting  as  very  delicate  seedlings. 

Of  the  1920  surface  sowing  (p.  43),  Koeleria  alone  survived  the  first  sum¬ 
mer  on  the  low  prairie,  but  was  then  winterkilled.  At  Nebraska  City,  4 
species,  Andropogon  scoparius,  A.  nutans,  Bouteloua  hirsuta,  and  Elymus  cana¬ 
densis  survived.  During  1921  a  single  small  weak  survivor  of  B.  hirsuta 
remained  alive  until  July  15,  when  it  succumbed.  The  other  species  had 
become  indistinguishable  from  the  general  plant  cover  by  midsummer. 

Trench  Sowing. 

Plants  in  the  trench  at  Nebraska  City  did  even  more  poorly  than  those  on 
the  surface.  Aristida  purpurea,  Bouteloua  gracilis,  B.  hirsuta,  Liatris  scari¬ 
osa,  Pinus  ponder  osa,  and  Stipa  spartea  did  not  germinate,  squirrels  having 
eaten  the  seeds  of  Pinus.  By  June  24,  Elymus  canadensis,  Liatris  punctata, 
and  Sporobolus  asper,  all  represented  by  a  few  plants  only,  had  died.  Calamo- 
vilfa  longifolia,  which  had  germinated  abundantly,  also  succumbed  in  July. 
Bouteloua  racemosa  survived  the  first  season,  tillered  rather  freely,  and  reached 
a  height  of  4  to  7  inches;  however,  it  was  winterkilled.  Andropogon  nutans 
alone  survived,  and  it  was  represented  by  a  good  stand  that  had  reached  a 
height  of  10  to  15  inches  by  fall. 

Out  of  11  species  planted  in  a  trench  on  the  gravel-knoll  April  20,  Aristida, 
B.  gracilis,  Koeleria,  Lespedeza,  and  Liatris  scariosa  failed  to  germinate.  A 
few  of  each  of  the  following  species  germinated,  the  two  last  dying  almost  at 
once  and  the  rest  during  June:  Elymus,  Liatris  punctata,  Sporobolus,  Stipa 
viridula.  Pinus  died  in  July  and  Andropogon  nutans  alone  survived,  being 
represented  by  a  few  plants  4  to  5  inches  tall  in  September.  These  lived 
over  the  winter,  but  were  doing  poorly  in  May  1922,  and  all  died  in  June. 
Six  of  the  8  species  planted  in  the  low-prairie  trench  germinated,  but  Bouteloua 
gracilis,  Lespedeza  capitata,  and  Liatris  punctata  died  soon  after.  Elymus 
canadensis  succumbed  to  dense  shading  in  June,  and  Stipa  viridula,  which 
was  represented  by  only  3  delicate  plants,  in  July.  Aristida  purpurea,  simi¬ 
larly  undeveloped  and  few  in  number,  consisted  of  a  few  remnants  4  to  6 
inches  tall  in  late  summer,  but  unfortunately  these  were  dug  up  in  trans¬ 
planting  sods. 

Of  the  seedings  in  the  trench  on  the  gravel-knoll  during  1920,  Andropogon 
scoparius  and  A.  nutans  were  the  only  survivors,  and  these  were  in  a  very 
poor  condition.  Both  made  a  feeble  growth  and  died  late  in  June  1921. 
In  the  low-prairie  trench,  4  species  survived  the  first  season  (1920),  but  all 
showed  the  effects  of  shading.  Of  these,  Stipa  viridula  and  Bouteloua  hir¬ 
suta  made  a  poor  growth  the  next  spring  and  died  in  July.  Andropogon 
nutans  and  Elymus  canadensis,  although  much  attenuated,  made  a  good 
growth,  reaching  heights  of  12  to  15  inches.  In  1922  a  small  clump  of  each 
reached  a  height  of  about  32  inches,  but  neither  blossomed,  owing  to  the 


EDAPHIC  STATIONS:  CULTIVATED  AREAS. 


75 


dense  shade.  However,  the  following  summer  both  blossomed  at  a  height 
of  2.5  feet.  At  Nebraska  City  all  but  4  of  the  1920  species  planted  in  the 
trench  survived,  but  Bouteloua  gracilis  died  the  following  winter.  Liatris 
punctata  and  Elymus  were  both  quite  abundant  in  May  1921,  but  succumbed 
during  June  and  July.  Andropogon  nutans  and  A.  scoparius  came  through 
the  second  season  in  a  thriving  condition,  reaching  a  height  of  5  to  9  inches. 
A  sparse  growth  of  Bouteloua  hirsuta  also  survived  the  season,  but  the  plants 
were  quite  delicate.  During  1922,  Bouteloua  succumbed  during  August 
drought,  after  making  a  good  growth  earlier.  The  two  Andropogons  formed 
good  sods  10  to  13  inches  tall;  both  grew  well  in  1923,  but  neither  blossomed. 

Growth  in  Cultivated  Soil. 

Native  species  made  remarkable  development  when  grown  in  narrow  rows 
(trench  method)  in  fertile  cultivated  soil,  kept  at  a  favorable  holard  at  all 
times,  and  free  from  competing  species  (table  27).  These  were  planted  on 
April  22  and  23  on  a  level  area  of  soil,  the  physical  and  chemical  composition 
of  which  was  almost  identical  with  that  of  the  cultivated  lowland  area  already 
described  (p.  41).  Potatoes  had  been  grown  on  the  area  the  preceding  year. 
A  month  before  planting  a  good  seed-bed  was  formed  by  plowing  and  repeated 


Table  27. — Growth  of  species  in  cultivated  soil ,  1921. 


Species. 

Aug.  2. 

Oct.  11. 

Agropyrum  glaucum .  .  . 

Excellent  growth,  14  in. 
tall. 

Excellent  growth,  IS  in.,  no  flower- 
stalks. 

Andropogon  nutans.  .  .  . 

Excellent,  24  to  32  in. 

Lvs.  2  ft.,  flower-stalks  3  to  5  ft., 
seed  ripe. 

Aristida  purpurea . 

Fine,  12  in.  tall. 

Fine  bunches  1  ft.,  flower-stalks  18 
to  20  in.,  abundant,  seed  ripe. 

Bouteloua  gracilis . 

Excellent,  1  ft.,  flower- 
stalks  to  2  ft.,  abundant 
blooming. 

Lvs.  16  to  18  in.,  flower-stalks  23  to 
33  in.,  seed  ripe. 

Bromus  inermis . 

Good  10  to  15  in. 

Lvs.  9  in.,  dense  growth,  flower-stalks 
18  in. 

Calamovilfa  longifolia . . 

Excellent  20  to  24  in. 

Fine  development,  24  to  27  in. ; 
flower-stalks  3  to  5  ft.;  seed  ripe. 

Elymus  canadensis .... 

Fine,  flower-stalks  2  to  2.5 
ft.,  heads  5  to  5.5  in. 
long. 

Fine  15  to  18  in.,  heads  abundant  at 
30  in. 

Gleditsia  triacanthus. . . 

Good,  7  to  14  in. 

Good,  13  to  20  in.,  stems  7  to  10  mm. 
diameter. 

Lespedeza  capitata .... 

Good,  4  to  5  in. 

Good,  5  to  6  in. 

Liatris  punctata . 

Good,  none  over  5  in. 

Good,  4  to  6  in.,  max.  of  7  lvs. 

Muhlenbergia  pungens . 

Excellent,  6  in. 

Flower-stalks  15  to  18  in.  seeded; 
bunches  12  to  16  in.  diameter,  8- 
in.  lvs. 

Onagra  biennis . 

Rosettes  abundant,  2  to  3 
in.  tall,  6  to  7  Ivs. 

Rosettes  5  to  8  in.  diameter,  2  to  3 
in.  tall. 

Robinia  pseudacacia .  . . 

2  to  3.5  ft.,  excellent. 

5  to  5.5  ft.  stems  over  0.5  in.  diam¬ 
eter. 

Sporobolus  asper . 

Excellent,  20  in. 

Bunches  3  to  3.5  in.,  flower-stalks 
abundant,  3  to  4  ft.,  seed  ripe. 

Stipa  spartea . 

Good  growth . 

Lvs.  15  to  22  in.,  very  broad;  no 
flower-stalks. 

Stipa  viridula . 

20  to  22  in.,  fine. 

Excellent;  no  flower-stalks. 

76 


EXPERIMENTS  DURING  1921. 


harrowing  (Weaver,  Jean,  and  Crist,  1920,  p.  80).  The  growth  made  during 
the  first  season  by  Andropogon  nutans  and  Calamovilfa  longifolia  is  shown  in 
plate  10b  and  11a,  and  that  of  Bouteloua  gracilis  in  plate  11b. 

Root  Development  at  Lincoln. 

Pinus  ponder osa  reached  a  height  of  1.5  inches  when  45  days  old  (June  6). 
The  first  whorl  of  leaves  was  as  long  as  the  cotyledons,  while  the  strong, 
vertically  descending  tap-root  had  penetrated  to  a  depth  of  13  inches.  The 
root  was  1  mm.  in  diameter,  brown  in  color,  and  had  no  laterals  over  4  cm. 
long.  These  were  usually  about  2  cm.  in  length,  white  near  the  end,  and 
entirely  unbranched  (fig.  34).  Liatris  punctata  of  similar  age  had  a  single 
leaf,  2  to  4  inches  high,  m  addition  to  the  cotyledons.  The  glistening  white 
tap-roots,  which  had  already  stored  some  food  in  their  enlarged  upper  parts, 
tapered  rapidly  and  reached  depths  of  10  to  16  inches.  They  descended  almost 
vertically  and  gave  off  but  few  short,  unbranched  laterals  (fig.  35). 


Robinia  pseudacacia  seedlings  45  days  old  had  about  6  compound  leaves  and 
a  height  of  5  inches.  The  tap-roots,  which  were  about  1  mm.  in  diameter, 
tapered  rapidly,  but  regained  their  maximum  diameter  again  in  the  vigorously 
growing  unbranched  portion  of  the  tip.  The  much  branched  tap-root  de¬ 
scended  irregularly  to  a  depth  of  12  to  15  inches;  branching  began  about  an 
inch  below  the  surface  and  continued  at  the  rate  of  10  to  20  per  inch,  some  of 
the  horizontal  laterals  having  a  spread  of  5  inches  (fig.  36). 

The  root  development  of  Gleditsia  triacanthus  was  even  more  remarkable. 
On  July  12,  when  81  days  old,  the  trees  had  a  height  of  7  to  9  inches  and 
15  to  17  compound  leaves.  The  tap-roots  reached  depths  of  30  to  40  inches. 
The  course  was  rather  directly  downward,  long  branches  being  given  off 
profusely  to  a  depth  of  20  inches.  Below  this  for  9  to  12  inches  many  shorter 


EDAPHIC  STATIONS:  ROOT  DEVELOPMENT. 


77 


ones  arose,  while  for  the  rest  the  tap-root  was  unbranched.  The  great  spread 
of  the  longer  horizontal  laterals  (12  to  18  inches),  their  large  number  and 
their  characteristic  branches,  which  as  often  pursued  an  upward  as  a  down¬ 
ward  course,  are  shown  for  one  of  the  largest  and  best  developed  root  sys¬ 
tems  in  figure  37. 

The  rosettes  of  Onagra  biennis 
were  5  to  8  inches  in  diameter  and 
2  to  3  inches  tall  on  October  5. 

The  glistening  white  tap-roots,  5 
or  6  mm.  in  diameter,  penetrated 
downward  in  a  somewhat  devious 
course,  tapering  to  1  mm.  in  width 
at  1.5  feet,  but  reaching  a  depth  of 
39  to  44  inches  in  the  stiff  wet  clay. 

Branches  to  the  number  of  100 
were  produced  just  below  the  soil 
surface  and  extended  to  a  depth 
of  1  foot.  These  varied  from  1  cm. 
to  6  inches  in  length  in  a  few;  they 
ran  off  rather  horizontally  and 
were  poorly  rebranched.  Below  a 
foot  the  branching  was  much  less 
pronounced  (3  to  6  per  inch  of 
tap-root)  and  the  laterals  short. 

In  the  deeper  soil  the  tap-root  took 
on  the  appearance  of  a  delicate 
white  thread. 

Near  the  end  of  the  growing- 
season  (October  5  and  6),  the  root  Fig.  36. — Robinia  pseudacacia  2.5  months  old. 

development  was  examined  in 

Muhlenbergia  pungens  and  Calamovilfa  longifolia,  both  characteristic  sand¬ 
hill  species  but  growing  here  in  rich  silt-loam.  The  former  was  repre¬ 
sented  by  bunches  12  to  16  inches  in  diameter  and  about  8  inches  in 
average  height.  Flower-stalks  15  to  18  inches  tall  were  abundant  (plate 
12a).  The  root  development  was  marked,  roots  being  traced  in  the  clay  sub¬ 
soil  to  a  maximum  depth  of  2.5  feet;  they  were  very  abundant  in  the  first  22 
inches.  Many  new  roots,  with  thick,  white,  rapidly  growing  tips  ended  in  the 
first  foot,  some  of  these  originating  from  the  prostrate  stems.  All  branched 
profusely  upon  entering  the  soil.  However,  there  were  not  so  many  surface 
roots  as  described  for  sandhill  specimens  (Weaver,  1920 : 89),  but  this  may  have 
been  due  to  the  age  of  the  plants.  Fine  laterals  were  exceedingly  numerous, 
as  many  as  30  to  50  per  linear  inch.  While  most  of  these  were  only  1  cm.  or 
less  in  length,  others  were  8  to  9  cm.  long  All  were  profusely  and  minutely 
branched,  the  larger  ones  to  the  third  and  fourth  order,  many  even  to  the 
tips,  although  some  that  were  growing  rapidly  were  wide  and  free  from 
branches. 

Calamovilfa  longifolia  had  made  an  excellent  growth,  having  leaves  24  to 
27  inches  high  and  an  abundance  of  flower-stalks  at  24  to  27  inches.  Many 
tough,  wiry  rhizomes,  thickly  covered  with  long  scales  and  tipped  with  buds 
an  inch  long  with  very  sharp,  hard  points,  extended  out  on  all  sides  of  the 


78 


EXPERIMENTS  DURING  1921. 


clumps  for  distances  of  6  to  8  inches.  Multitudes  of  tough,  wiry  roots  pene¬ 
trated  the  soil  vertically  or  obliquely  downward  to  depths  of  5  feet  and  some 
extended  beyond  a  depth  of  6  feet.  Beginning  just  below  the  soil-surface  and 
extending  to  near  the  tips  of  the  larger  roots,  laterals  well  provided  with 


Fig.  37. — Root  system  of  Gleditsia  triacanthus  less  than  3  months  old. 


branches  to  the  third  and  fourth  order  were  abundant.  Most  of  the  major 
laterals  were  only  an  inch  or  two  long,  but  with  the  main  roots  they  thoroughly 
occupied  the  soil  beneath  and  for  several  inches  on  all  sides  of  the  clumps 
(plate  12,  a  and  b). 

The  excellent  growth  of  all  of  these  native  species  under  favorable  condi¬ 
tions,  73  per  cent  of  the  grasses  bearing  seed  the  first  season,  emphasizes  the 
keen  competition  prevailing  in  stabilized  grassland. 

Sowing  in  Denuded  Quadrats. 

Fourteen  species  were  planted  in  denuded  quadrats  on  the  gravel-knoll, 
April  14.  Koeleria,  Liatris  'punctata,  L.  scariosa,  and  Muhlenbergia  pun - 


EDAPHIC  STATIONS:  DENUDED  QUADRATS. 


79 


gens  did  not  germinate,  while  Lespedeza  capitata,  Pinus  ponderosa,  Sporo- 
bolus  asper,  and  Stipa  viridula  germinated  in  small  numbers  (except  the  last, 
which  was  abundant),  but  all  died  before  the  end  of  June.  At  this  time  the 
mortality  among  the  remaining  species  was  also  pronounced.  Bouteloua 
gracilis  and  Cala7novilfa  longifolia  died  in  August.  Symphoricarpus  vulgaris, 
which  was  propagated  from  transplanted  rhizomes,  was  nearly  dead;  Elymus 
canadensis  was  represented  by  a  single  plant  9  inches  tall,  Aristida  purpurea  by 
4  small  clumps,  and  Andropogon  nutans,  which  had  formed  a  thin  sod,  was  in 
poor  condition.  Thus,  while  71  per  cent  of  the  species  germinated  or  grew 
from  rhizomes,  only  40  per  cent  of  these  survived  the  first  summer.  Of  the  16 
species  sown  in  the  low  prairie,  Koeleria,  Liatris  punctata,  L.  scariosa,  and 
Symphoricarpus  vulgaris  failed  to  germinate  or  grow.  Stipa  viridula  died 
during  June,  but  the  other  species  (except  Robinia  pseudacacia,  which  died 
in  August)  lived  throughout  the  summer.  Nearly  all  made  a  fair  growth, 
but  showed  the  effects  of  shading,  the  trees  having  thin,  broad,  pale  leaves, 
while  those  of  several  of  the  grasses  were  much  attenutaed. 

At  Nebraska  City,  7  of  the  22  species  failed  to  germinate.  The 
seeds  of  Pinus  ponderosa  had  been  dug  up  and  eaten  by  squirrels.  Bouteloua 
gracilis,  Lespedeza,  Liatris  scariosa,  and  Muhlenbergia  died  in  June,  as  did  also 
Bromus  inermis  and  Elymus  canadensis,  both  of  which  were  eaten  to  the 
ground  by  grasshoppers.  All  of  the  others  made  good  growth,  shading  at  this 
station  being  less  pronounced  than  on  the  low  prairie.  Andropogon  nutans 
formed  a  dense  sod  (plate  13).  Calamovilfa  was  all  dead  but  a  few  plants,  and 
Robinia  was  represented  by  a  single  seedling,  grasshoppers  having  damaged 
the  good  stand  of  early  summer. 

On  the  low  prairie  all  the  species  germinated  and  all  but  one  came  through 
the  season  in  excellent  condition.  Stipa  setigera  (seed  from  California) 
was  winterkilled;  the  rest  made  a  fine  growth  until  the  end  of  July,  Aris¬ 
tida  and  both  species  of  Bouteloua  blossoming.  Andropogon  scoparius,  A. 
nutans,  A.  furcatus,  Koeleria,  and  Elymus  formed  good  sods  and,  like  Stipa 
viridula,  had  tillered  heavily.  A.  scoparius,  A.  nutans,  A.  furcatus,  and 
Elymus  continued  to  thrive,  reaching  heights  of  18  to  24  inches,  Koeleria  grew 
to  a  height  of  7  to  11  inches,  and  Bouteloua  gracilis  and  B.  hirsuta  put  forth 
flower-stalks  18  to  20  inches  tall.  Stipa  viridula  was  so  badly  shaded  that  half 
of  the  plants  died,  as  did  nearly  all  the  tips  of  the  leaves  on  the  remaining 
plants.  Autumn  found  Aristida  purpurea  also  nearly  dead  or  dying.  In  1922, 
one  lot  of  Aristida  died  in  May  and  one  of  Stipa  in  June,  while  Bouteloua 
hirsuta  succumbed  in  August.  Although  the  others  made  a  good  growth  for  the 
most  part,  Andropogon  nutans,  A.  scoparius,  Aristida,  Bouteloua  gracilis,  and 
Elymus  alone  flowered.  During  the  summer  of  1923,  Aristida,  Bouteloua 
gracilis,  Stipa  viridula,  and  one  lot  of  Koeleria  died  as  a  result  of  the  dense 
shade.  While  all  three  andropogons  showed  a  normal  development  and 
formed  dense  sods,  Koeleria  and  Elymus  were  clearly  losing  ground. 

At  Nebraska  City,  all  of  the  species  in  the  1920  quadrats  germinated, 
became  established,  and  lived  throughout  the  summer.  However,  the 
mortality  among  the  individuals  was  high  and  in  general  the  stand  was 
not  as  good  as  on  the  low  prairie.  All  but  Koeleria  survived  the  second 
season.  Grasshoppers  kept  this  species  eaten  back  and  also  made  consider¬ 
able  ravages  on  Stipa  viridula,  Liatris  punctata,  and  Elymus.  Most  of  the 


80 


EXPERIMENTS  DURING  1921. 


grasses  tillered  heavily,  but  no  sod  was  formed  comparable  to  that  on  the 
low  prairie.  Neither  did  they  make  an  equal  height-growth,  Andropogon 
reaching  heights  of  only  8  to  15  inches  and  Bouteloua  4  to  10  inches.  Andro¬ 
pogon  scoparius  and  Bouteloua  hirsuta  were  the  only  species  that  seeded. 
Stipa  viridula  was  winterkilled  in  1921-22,  but  all  the  rest  came  through  the 
following  summer.  Aristida  and  Elymus  did  poorly,  but  the  others  made 
fair  to  excellent  growth,  although  flower  production  was  not  common,  prob¬ 
ably  owing  in  part  to  the  dry  fall.  These  3-year-old  quadrats  were  mostly 
invaded  by  Poa  pratensis,  species  of  Car  ex,  and  Helianthus  rigidus,  but  none 
to  the  extent  of  causing  serious  competition.  In  1922-23,  Elymus  was  winter- 
killed,  while  all  the  others  not  only  made  a  very  good  growth,  but  some  also 
produced  seed. 

At  Colorado  Springs,  7  of  the  9  species  planted  in  denuded  quadrats  in 
1920  germinated,  and  of  these  4  survived  the  first  season.  During  1921, 
Andropogon  nutans  and  Elymus  canadensis  died,  but  Andropogon  scoparius 
formed  an  open  tufted  sod  2  inches  high,  which  covered  nearly  the  whole 
quadrat  and  reached  a  height  of  4  inches  by  1923.  Stipa  viridula  also  did 
well,  tillering  freely  and  reaching  heights  of  6  and  12  inches  in  1922  and 
1923  respectively. 

Root  Development  at  Peru,  Nebraska. 

A  number  of  species  were  grown  in  a  well-prepared  seed-bed  in  a  cultivated 
field  near  Peru,  Nebraska,  a  station  about  20  miles  south  of  Nebraska  City. 
The  mellow  silt-loam  soil,  underlaid  at  a  depth  of  1  to  1.5  feet  with  a  loess 
of  very  loose  texture,  not  only  absorbs  water  readily,  but  has  a  high  water¬ 
holding  capacity.  This  ranges  from  57  to  64  per  cent  and  is  rather  uniform 
to  a  depth  of  at  least  4  feet,  the  same  type  of  subsoil  extending  to  depths  of 
many  feet.  The  mechanical  analysis  of  this  soil  shows  that  it  is  approximately 
one-half  silt,  while  the  remainder  is  composed  almost  entirely  of  very  fine  sand 
and  clay.  Weaver  has  shown  that  in  this  soil-type  roots  of  species  common 
to  both  true  and  subclimax  prairie  penetrate  more  deeply  than  in  the  stiffer 
silt  loam  at  Lincoln  (1919:15).  Normally,  the  rainfall  is  about  5  inches 
greater  than  at  Lincoln;  however,  during  1921  it  was  not  only  deficient,  but 
also  poorly  distributed.  During  April,  the  rainfall  was  nearly  3  inches  below 
normal,  70  per  cent  of  it  falling  at  one  time.  For  May  it  was  1.6  inches  below 
normal,  72  per  cent  of  it  falling  between  May  7  and  10.  June,  with  3.4 
inches  of  precipitation,  practically  all  of  which  occurred  before  the  middle  of 
the  month,  had  a  deficiency  of  1.4  inches.  The  holard  was  much  below  nor¬ 
mal  and  the  poor  growth  of  crops  marked  the  season  as  one  of  distinct  drought 
(Weaver,  Jean,  and  Crist,  1922:78),  though  the  native  species  made  a  fairly 
good  growth.  When  they  had  reached  an  age  of  90  days  (July  18-19),  the 
development  of  the  plants  both  above  and  below  ground  was  recorded  (table 
28).  The  development  below  ground  was  marked  and  agreed  well  with  pre¬ 
vious  findings  as  to  the  deep-seated  nature  of  mature  root  systems  in  this 
mellow  loess  soil. 

Seedling  Transplants. 

Seedlings  of  14  species  were  transplanted  to  the  gravel-knoll  on  May  9. 
Agropyrum  glaucum,  Aristida  purpurea,  and  Stipa  viridula  had  died  by  May 
25,  Elymus  canadensis  and  Koeleria  cristata  succumbed  early  in  June,  and 


EDAPHIC  STATIONS!  SUMMARY. 


81 


Bouteloua  racemosa  and  Stipa  comata  later  in  the  month.  Liatris  punctata 
and  Stipa  spartea  died  in  July  and  Andropogon  furcatus  in  August.  By  the 
end  of  the  summer  Bouteloua  gracilis  and  Liatris  scariosa  were  represented 
by  remnants  only,  and  both  species  died  later  in  the  year.  Bouteloua  hirsuta 
came  through  the  summer  with  only  one  small  clump  about  3  inches  tall  and 
Andropogon  nutans  with  two,  6  or  7  inches  high,  the  survival  for  the  first 
season  being  14  per  cent. 


Table  28. — Development  of  seedlings  at  Peru ,  Nebraska,  July  19,  1921. 


Species  planted 
Apr.  19. 

Development 
of  shoots. 

Work¬ 
ing 
depth 
of  roots. 

Maxi¬ 
mum 
depth 
of  roots. 

Lateral 

spread 

of 

roots. 

in. 

in. 

in. 

Andropogon  nutans. . 

Good  stand;  luxuriant  growth;  ave. 
height  11  in.;  max.  height  16  in. 

36 

48 

Aristida  purpurea.  .  . 

Good  growth;  height  4  to  6  in.;  12  to  30 
tillers  per  plant. 

26 

41 

•  • 

Bouteloua  gracilis.  .  . 

Good  stand;  lvs.  4  to  8  in.  high;  exceed¬ 
ingly  well  tillered;  flower-stalks  about 

9  in.  tall. 

22 

37 

8 

Elymus  canadensis.  . 

Vigorous  plants;  height  10  to  16  in.;  3 
to  4  tillers  per  plant;  heads  appearing. 

27 

42 

9 

Liatris  punctata . 

Good  growth;  3  to  5  leaves  per  plant; 

3  to  4  in.  tall. 

47 

Stipa  viridula . 

Thin  stand,  vigorous  growth,  ave.  height 

7  to  9  in.;  6  to  10  tillers  per  plant. 

18 

26 

12 

Seedlings  that  were  transplanted  to  low  prairie  at  the  same  time  made  a 
much  better  growth.  All  grew  well,  but  by  the  end  of  June  Agropyrum,  Boute¬ 
loua  racemosa,  and  Elymus  particularly,  showed  the  effects  of  shading.  In 
July,  through  error,  a  part  of  the  prairie  into  which  the  transplant  area  ex¬ 
tended  was  mown.  Those  in  the  area  of  better  illumination  made  a  fine 
growth,  the  shorter  boutelouas  reaching  heights  of  4  to  8  inches  and  the 
andropogons  6  to  12  inches.  In  the  shaded  area  Agropyrum  died  and  the 
other  species  made  but  a  poor  to  fair  growth,  the  leaves  being  thin  and  atten¬ 
uated;  the  loss  of  only  1  of  the  13  species  is  remarkable. 

All  of  the  seedling  transplants  at  Nebraska  City  did  very  well  until  about 
the  middle  of  June,  when  Agropyrum,  Koeleria,  and  Liatris  punctata  died 
and  by  July  15,  Bouteloua  racemosa  had  likewise  succumbed.  The  other 
boutelouas,  Aristida,  and  the  andropogons,  however,  were  in  a  flourish¬ 
ing  condition.  Elymus,  Stipa  comata,  and  S.  viridula  had  been  badly  eaten 
back  by  grasshoppers  and  were  represented  by  remnants  only,  as  were  also 
Liatris  scariosa  and  S.  spartea.  Elymus  and  Stipa  viridula  died  in  August, 
and  S.  comata  was  found  to  be  in  very  poor  condition  in  the  autumn,  but  the 
other  7  species  were  doing  quite  well. 

Summary. 

A  summary  of  the  experiments  for  this  year  is  given  in  table  29.  The 
results  from  the  Colorado  Springs  station  are  omitted  because  the  area  was 
broken  into  by  cattle  and  closely  grazed.  Owing  to  the  drought  at  Nebraska 
City,  the  percentage  of  germination  is  lower  here  than  in  low  prairie  at  Lin- 


82 


EXPERIMENTS  DURING  1921. 


coin.  However,  the  percentage  of  establishment  averaged  slightly  higher 
at  the  Nebraska  City  station,  although  growth  was  somewhat  poorer.  The 
germination  averaged  slightly  lower  on  the  gravel-knoll  (where  surface  sow¬ 
ing  was  omitted)  than  at  Nebraska  City,  while  the  establishment  was  decidedly 


Table  29. — Summary  of  sowing  experiments,  1921. 


Method  of 
planting. 

Percentage  of  germination. 

Percentage  of  germinated  species 
established. 

Gravel- 

knoll. 

Low 

prairie. 

Nebraska 

City. 

Gravel- 

knoll. 

Low 

prairie. 

Nebraska 

City. 

Surface . 

78 

78 

14 

29 

Trench . 

55 

75 

50 

17 

17 

33 

Denuded  quadrat. . . . 

71 

75 

68 

40 

83 

60 

Average . 

63 

76 

65 

29 

38 

41 

Seedlings . 

•  • 

14 

92 

57 

lower.  The  survival  of  transplanted  seedlings  was  highest  on  low  prairie 
(92  per  cent),  intermediate  at  Nebraska  City  (57  per  cent),  and  least  on  the 
gravel-knoll  (14  per  cent). 

Of  the  survivors  of  the  surface-sown  species  of  the  preceding  year  (1920)  on 
low  prairie,  Koeleria  was  winterkilled.  One  of  the  4  survivors  at  Nebraska 
City  died.  Of  those  sown  in  the  trench,  both  survivors  of  1920  on  the  gravel- 
knoll  died,  2  of  the  4  on  low  prairie,  and  3  of  the  6  at  Nebraska  City. 
Among  the  species  planted  in  the  denuded  quadrats  during  1920,  none 
persisted  on  the  gravel-knoll.  One  of  the  10  survivors  on  the  low  prairie 
died  during  1921,  and  also  1  of  the  10  at  Nebraska  City. 


Table  30. — Comparison  of  germination  and  growth  at  the  several  stations,  1921. 


Average  per  cent  of  germination. 

Average  per  cent  of  establishment  of 
germinated  species. 

Lincoln  high  prairie .  81 

Lincoln  low  prairie .  76 

Phillipsburg .  68 

Nebraska  City .  65 

Lincoln  gravel-knoll .  63 

Burlington .  43 

Phillipsburg .  65 

Nebraska  City .  41 

Lincoln  high  prairie .  40 

Lincoln  low  prairie .  38 

Gravel-knoll .  29 

Burlington .  7 

Per  cent  of  establishment  in  denuded 
quadrats: 

Per  cent  of  establishment  of  seedlings: 

Lincoln  low  prairie .  83 

Lincoln  high  prairie .  65 

Phillipsburg .  63 

Nebraska  City .  60 

Gravel-knoll .  40 

Burlington .  21 

Lincoln,  low  prairie .  92 

Phillipsburg . , .  75 

Nebraska  City .  57 

Lincoln,  high  prairie .  54 

Gravel-knoll .  14 

Burlington .  0 

If  the  data  from  the  other  stations  are  included  and  arranged  in  the  order 
of  the  average  percentage  of  germination  (table  30),  they  prove  to  be  in 
general  agreement  with  those  of  the  preceding  year  (p.  48),  with  two  excep¬ 
tions.  Owing  to  the  drought,  Nebraska  City  ranks  after  Phillipsburg,  in¬ 
stead  of  heading  the  list,  while  Phillipsburg  falls  behind  low  prairie  in  rank. 

When  the  stations  are  arranged  according  to  the  average  percentage  of 
establishment,  Phillipsburg  ranks  highest  with  65  per  cent  (largely  because 


EDAPHIC  STATIONS!  SOD  TRANSPLANTS. 


83 


of  the  excellent  establishment  of  surface-sown  plants).  The  Lincoln  stations 
and  Nebraska  City  are  about  the  same  (38  to  41  per  cent),  while  the  gravel- 
knoll  and  Burlington  have  changed  in  relative  position,  the  latter  giving  the 
lowest  percentage  of  establishment.  On  the  basis  of  establishment  in  de¬ 
nuded  quadrats,  the  same  sequence  occurs  as  during  1920,  except  that  Ne¬ 
braska  City  then  ranked  first  and  the  gravel-knoll  last.  If  an  average  is 
obtained  from  all  four  criteria  for  growth,  the  stations  aline  them¬ 
selves  as  follows:  Low  prairie  72,  Phillipsburg  67,  high  prairie  60,  Nebraska 
City  56,  gravel-knoll  37,  and  Burlington  18. 

Sod  Transplants. 

Gravel-knoll. 

Between  March  20  and  31,  18  blocks  of  sod,  including  14  species  from 
the  various  Lincoln  stations,  were  transplanted  to  the  gravel-knoll. 
Distichlis  spicata  died  in  June,  while  Agropyrum  glaucum,  Andropogon  sco- 
parius,  and  two  lots  of  Koeleria  cristata  died  during  August,  notwithstanding 
the  relatively  favorable  season  for  growth.  With  the  exception  of  Poa 
pratensis,  all  of  the  other  species  made  a  fair  growth,  but  the  scarcity  of  water 
was  indicated  by  the  rolling  of  leaves  and  frequent  wilting  (table  25).  Andro¬ 
pogon  furcatus  and  A.  nutans  reached  a  height  of  a  foot  and  Panicum  virgatum 
one  of  1.5  feet,  but  did  not  put  forth  flower-stalks.  Bouteloua  hirsuta  and 
racemosa  had  a  few  flower-stalks  each  at  1  and  2  feet  respectively,  while 
Bulbilis  blossomed  profusely  in  June,  but  like  the  other  species  did  not 
increase  its  area.  Elymus  bore  several  fine  heads  at  a  height  of  2  to  2.5  feet 
and  Spartina  cynosuroides  from  the  swamp  flowered  at  27  to  34  inches;  Poa 
and  Stipa  also  blossomed. 

Poa  and  both  clumps  of  B.  racemosa  were  winterkilled.  Elymus  died  during 
the  August  drought,  but  all  of  the  others  made  a  fair  to  good  growth,  although 
adversely  affected  by  the  late  summer  drought.  Seven  of  the  8  species  bloomed, 
Andropogon  furcatus  from  the  low  prairie  alone  failing  to  put  forth  flower- 
stalks.  All  survived  the  drought  of  the  following  fall  and  winter.  Panicum 
alone  made  a  poor  growth  the  following  season,  while  Andropogon  furcatus , 
Bulbilis ,  and  Spartina  spread  a  foot  or  more  beyond  their  original  area.  By 
August  25,  Stipa  and  Bulbilis  were  the  only  species  that  gave  signs  of  having 
flowered  or  preparing  to  flower,  a  striking  contrast  to  the  preceding  year, 
when  drought  promoted  reproduction.  Even  during  the  very  favorable  year 
of  1923,  but  more  especially  during  preceding  seasons,  sod  transplants  on  the 
gravel-knoll  were  all  much  shorter  than  elsewhere.  They  also  began  renewed 
development  earlier  and  produced  flower-stalks  sooner. 

Of  the  species  planted  in  the  spring  of  1920,  although  suffering  severely 
from  drought,  only  one  sod  of  Poa  and  another  of  Andropogon  scoparius  in 
the  unwatered  row  died  (table  66).  One  of  Koeleria  was  winterkilled,  while 
a  sod  of  Elymus  and  another  of  Koeleria  died  during  August  of  the  second 
season.  Practically  all  of  the  species,  including  Panicum  virgatum  and 
Spartina  cynosuroides,  made  a  fair  growth,  rolling  of  leaves  and  wilting 
occurring  much  more  rarely  than  in  transplants  of  the  current  year,  owing  to 
the  well-established  root  systems.  Exceptions  to  this  occurred  in  the  case  of 
Agropyrum,  both  lots  of  which  did  very  poorly,  as  did  also  one  sod  of  Elymus 
and  the  remaining  block  of  Koeleria.  After  the  middle  of  August,  when  the 


84 


EXPERIMENTS  DURING  1921. 


short-grass  cover  of  the  knoll  began  to  dry,  most  of  the  tail-grass  sods  began 
to  change  color  and  enter  the  winter  condition  also.  One  lot  each  of  A. 
furcatus,  A.  scoparius,  B.  racemosa,  Elymus  canadensis,  and  Poa  pratensis  and 
all  three  lots  of  Panicum  virgatum  had  flowered  and  set  seed,  although  the 
flower-stalks  were  fewer  in  number  and  smaller  than  normal.  Of  the  species 
that  seeded  the  first  season  after  transplanting,  viz,  Koeleria,  Stipa,  Agro- 
pyrum,  Elymus,  Panicum,  and  Poa,  only  the  last  three  seeded  the  second 
year.  The  single  remaining  lot  of  Koeleria  and  Poa  were  both  winterkilled 
and  one  Agropyrum  died  in  June  1922.  Both  lots  of  Elymus  died  later  in  the 
summer,  as  did  also  one  of  Andropogon  furcatus.  The  effect  of  drought  upon 
the  other  species  is  shown  in  table  66.  So  well  were  these  species  rooted, 
however,  that  the  dry  fall  and  winter  of  1922-23  took  but  a  single  Andropogon 
scoparius.  The  growth  during  1923  was  marked,  Panicum  doubling  and 
Andropogon  nutans  tripling  its  area. 

Low  Prairie. 

Fifteen  species  of  grasses  were  transplanted  into  the  low  prairie  late  in 
March  1921.  The  rank  growth  of  the  native  tail-grasses  produced  a  very 
dense  shade  (plate  6a).  Bouteloua  hirsuta,  Distichlis  spicata,  and  Koeleria 
cristata  had  died  by  late  summer  and  Agropyrum  had  made  but  poor  growth. 
Bouteloua  gracilis  and  Bulbilis  dactyloides  both  reached  a  height  of  12 
inches,  the  leaves  being  much  attenuated,  but  neither  was  able  to  increase 
its  territory.  Andropogon  furcatus,  A.  nutans,  Bouteloua  racemosa,  Spartina 
cynosuroides,  and  Stipa  spartea  all  developed  about  normally,  but  none  blos¬ 
somed.  Bulbilis,  Poa,  Andropogon  scoparius,  Elymus,  and  Panicum  bore 
well-developed  flower-stalks  and  seeded  rather  profusely.  During  the  follow¬ 
ing  May  and  June,  owing  to  the  dense  cover  and  resulting  competition, 
Andropogon  scoparius,  Bouteloua  racemosa,  B.  gracilis,  and  Stipa  spartea,  all 
high-prairie  species,  died.  Bulbilis  died  in  July,  while  by  the  end  of  the 
summer  Agropyrum,  one  Elymus ,  and  Poa  were  represented  by  remnants  only. 
Elymus,  Panicum,  and  Spartina  alone  blossomed.  All  these  survived  the  dry 
winter,  but  by  August  1923,  Agropyrum  was  dead  and  Poa  nearly  shaded  out. 
Both  lots  of  Elymus  were  heading  at  40  to  42  inches  high,  while  the  other 
subclimax  species,  viz,  Spartina,  Panicum,  Andropogon  nutans,  and  A. 
furcatus,  were  all  flourishing. 

As  to  the  1920  transplants  at  this  station,  all  made  a  good  growth,  and  all 
except  Spartina  cynosuroides  bloomed  (table  67).  By  May  18,  1921,  Bouteloua 
racemosa,  one  lot  of  Koeleria,  and  two  of  Stipa  spartea  were  dead.  Many 
others,  particularly  Agropyrum,  Bulbilis,  Distichlis,  and  Stipa,  were  suffer¬ 
ing  from  shading  and  invasion,  but  all  other  species  made  a  good  growth 
during  June  and  July.  By  the  end  of  the  summer,  one  Agropyrum  had 
died,  and  the  other  was  much  attenuated.  Bulbilis,  Distichlis,  and  Koeleria 
were  nearly  dead,  being  represented  by  remnants  only,  and  Bulbilis  alone  had 
blossomed.  However,  all  of  the  other  species  had  made  an  excellent  growth. 
The  three  andropogons  exhibited  abundant  flower-stalks  3  to  5  feet  high,  and 
Bouteloua  gracilis  had  leaves  a  foot  tall,  but  flowered  sparingly.  Elymus  and 
Panicum  possessed  flower-stalks  in  profusion  4  to  5  feet  tall,  and  Stipa  seeded 
at  33  to  36  inches,  while  Spartina  made  a  good  growth  but  did  not  blossom. 

By  May  of  the  following  spring  (1923),  one  Andropogon  scoparius  and 
Koeleria  had  died  in  addition  to  Distichlis.  Panicum  virgatum  and  Andro- 


EDAPHIC  STATIONS:  SOD  TRANSPLANTS. 


85 


pogon  nutans  and  one  lot  of  A.furcaius  were  indistinguishable  from  the  general 
cover.  Poa  pratensis  and  another  Andropogon  scoparius  died  in  July,  and 
Agropyrum  glaucum  and  Bulbilis  by  August.  At  this  time  the  following  were 
in  rather  poor  condition :  one  Andropogon  scoparius,  both  plants  of  Bouteloua 
gracilis,  and  Elymus  and  Koeleria,  but  the  rest  had  made  a  good  growth. 
By  the  spring  of  1923,  Bouteloua  gracilis  and  one  Andropogon  scoparius 
were  dead.  By  the  end  of  this,  the  fourth  season,  sufficient  time  had  elapsed 
for  a  fair  adjustment  of  the  species  to  the  low-prairie  habitat.  Although 
the  remaining  high-prairie  species  (two  lots  of  Stipa  and  one  of  Koeleria) 
were  still  in  fair  condition,  the  last  Andropogon  scoparius  was  in  straits. 
The  other  species  of  the  subclimax  prairie,  viz,  Andropogon  furcatus,  Elymus 
canadensis,  and  Spartina  cynosuroides,  were  flourishing,  while  Andropogon 
nutans  and  Panicum  virgatum  had  already  become  indistinguishable  from 
the  native  sod.  The  following  had  entirely  lost  out  in  the  struggle  for  light : 
Agropyrum,  Bouteloua  gracilis,  Bulbilis,  Poa,  Bouteloua  racemosa,  and  Dis- 
tichlis  spicata.  As  a  consequence,  these  experiments  clearly  reveal  the  effect 
of  competition  in  sorting  out  species  and  stabilizing  vegetation. 

Salt-flat. 

Sods  of  each  of  the  preceding  species  were  also  transplanted  into  the  salt-flat 
late  in  March,  1921.  During  June  most  of  the  plants  suffered  from 
drought,  great  cracks  appearing  on  the  sides  of  the  transplanted  blocks,  owing 
to  the  peculiar  nature  of  the  soil  (p.  44).  Growth  was  very  poor,  wilting  and 
even  dying  of  parts  being  not  uncommon.  Throughout  July,  growth  was 
slow,  most  of  the  sods  making  only  a  sparse  growth  and  Spartina  alone 
flourishing.  Koeleria  and  Stipa  failed  to  blossom  or  bore  only  a  few  dwarfed 
flower-stalks,  and  the  inflorescence  of  Bulbilis  was  also  shorter  than  normal. 
By  the  end  of  the  summer,  the  leaves  of  Andropogon  furcatus,  A.  nutans,  and 
Bouteloua  racemosa  were  dying  back,  while  Panicum  virgatum  and  B.  hirsuta 
were  nearly  dead.  These,  like  Agropyrum,  B.  gracilis,  and  Spartina,  had 
failed  to  blossom.  Andropogon  scoparius,  Elymus,  and  Poa  had  dwarfed 
flower-stalks  and  Distichlis  alone  developed  normally. 

As  a  result  of  the  drought  of  the  following  June,  all  the  sods  were  in  poor 
condition,  large  cracks  occurring  around  most  of  the  transplanted  blocks, 
even  those  that  had  been  transplanted  2  or  3  years,  and  many  of  them  were 
very  dry.  One  Koeleria  died  in  June  and  the  other  two  did  very  poorly. 
Poa  and  Panicum  were  represented  only  by  remnants  at  the  end  of  the  season 
and  the  growth  in  many  of  the  other  blocks  was  very  sparse.  Practically 
all  of  the  plants  were  dwarfed  and  only  4  species  blossomed,  viz,  Andropogon 
scoparius,  Bulbilis,  Elymus,  and  Koeleria;  on  these  the  inflorescences  were 
much  dwarfed. 

During  the  very  favorable  growing-season  of  1923,  another  Koeleria  and 
Stipa  died  and  Andropogon  furcatus,  A.  scoparius,  Bouteloua  racemosa,  Panicum 
virgatum,  and  Spartina  cynosuroides  were  represented  by  remnants  only. 
Seven  species  seeded,  although  not  abundantly. 

The  sods  transplanted  into  the  salt-flat  during  1920  made  a  poor  growth 
the  first  season,  though  8  of  the  13  species  blossomed  (table  68).  Compared 
with  the  growth  of  similar  species  in  the  adjoining  low  prairie,  nearly  all  were 
greatly  dwarfed.  However,  they  survived  the  first  season.  During  May 
1921,  Andropogon  scoparius,  A.  nutans,  Stipa  spartea,  one  lot  of  Elymus 


86 


EXPERIMENTS  DURING  1921. 


canadensis,  and  one  Koeleria  cristata  were  in  poor  condition  or  dying.  How¬ 
ever,  many  of  the  others,  including  Panicum  and  Spartina,  were  doing  quite 
well.  Throughout  June  and  July  they  grew  fairly  well,  except  A.  scoparius, 
which  was  mostly  dead  and  badly  invaded  by  Distichlis.  All  lived  through¬ 
out  the  second  season  but  Bouteloua  racemosa,  though  none  grew  normally 
except  Distichlis.  Agropyrum,  A.  scoparius ,  A.  nutans,  B.  racemosa,  Spar¬ 
tina,  and  Stipa  failed  to  flower.  The  dwarfed  condition  of  the  remaining 
species,  all  of  which  blossomed,  was  well  represented  by  A.  furcatus,  which 
bore  flower-stalks  only  about  2  feet  high.  Panicum  was  an  exception,  with 
a  few  stalks  reaching  a  height  of  40  inches,  but  its  vegetative  growth,  as  for 
all  of  the  other  species,  was  much  below  normal.  Elymus  canadensis  failed 
to  grow  in  1922,  while  one  Panicum  virgatum  died  in  June.  Although  the 
plants  in  general  made  a  fair  growth,  they  were  dwarfed  and  several 
species  did  poorly.  Andropogon  furcatus,  Distichlis,  Koeleria,  Panicum,  and 
Poa  blossomed.  Owing  to  an  excellent  holard,  all  the  species  except 
Elymus,  Stipa,  and  Andropogon  nutans  made  a  good  growth  during  1923. 
Consequently,  it  seems  evident  that  several  species  can  tolerate  the  saline 
areas  dominated  by  Distichlis  and  Agropyrum,  as  was  clearly  shown  during 
the  wet  year  of  1923.  As  a  result,  the  salt-basin  is  being  gradually  invaded 
by  various  prairie  species. 

Salt-basin. 

A  similar  lot  of  sods  was  transplanted  to  an  area  in  the  salt-basin  just  west 
of  Lincoln,  which  is  dominated  by  Dondia  depressa.  This  halophyte  occu¬ 
pies  an  intermediate  zone  between  the  less  saline  Distichlis  area  and  the  wetter 
and  more  saline  one  of  Salicornia  herbacea.  Repeated  analyses  of  the  soil 
in  the  Dondia  area  show  that  it  has  a  salt-content  of  1.8  to  2.0  per  cent,  prac¬ 
tically  all  of  which  is  sodium  chloride.  The  holard  in  spring  and  early  summer 
is  more  or  less  favorable  for  growth.  Dondia,  Salicornia,  and  Distichlis 
were  also  transplanted  early  in  April,  together  with  the  sods  of  the  grasses. 
Within  20  days  the  transplants  from  non-alkaline  soil  began  to  lose  their 
green  color  and  the  tips  of  the  leaves  to  dry,  and  after  another  20-day  period 
all  were  dead.  The  three  halophytes  did  very  well  throughout  the  season, 
except  Salicornia,  which  suffered  apparently  from  drought  late  in  the 
summer. 

Swamp. 

Sods  of  the  same  species  were  transplanted  into  the  swamp  in  March 
1921.  Owing  to  the  building  of  a  dam  higher  up  the  ravine,  conditions  were 
markedly  different  from  the  preceding  year.  The  soil  in  the  wettest 
area  was  not  saturated  to  the  surface  throughout  the  spring,  although  water 
stood  on  the  top  during  the  first  week  in  May.  For  much  of  the  remainder 
of  the  season  the  area  was  relatively  dry,  the  holard  being  so  low  that  water 
could  not  be  pressed  out  by  hand  from  the  surface  6  inches.  The  Poa  zone 
was  also  drier  than  the  preceding  year.  This  area,  which  was  nearly  pure 
bluegrass  at  the  beginning  of  the  experiments  (1920),  was  now  invaded  by  a 
rank  growth  of  Spartina,  and  light  conditions  were  less  favorable  than  for¬ 
merly. 

In  the  swamp  all  of  the  grasses  made  a  very  good  growth  until  the  end  of 
June,  Bulbilis  flowering  profusely,  but  Stipa  and  Koeleria,  other  early  bloom- 


EDAPHIC  STATIONS!  SOD  TRANSPLANTS. 


87 


ers,  failed  to  bloom.  At  this  time  Spartina  was  3  feet  high  all  around  the 
sods  and  the  transplants  began  to  show  the  effects  of  shading,  the  light  values 
falling  as  low  as  2  to  5  per  cent.  By  the  end  of  July  the  surrounding  vegeta¬ 
tion  was  4  feet  tall  and  some  of  the  sods  were  found  with  difficulty.  The 
soil  was  wet,  and  hence  many  of  the  plants  were  slender,  with  narrow  leaves. 
Late  in  August,  Agropyrum ,  Bouteloua  hirsuta,  B.  gracilis,  Distichlis,  and 
Koeleria  were  dying  back  or  mostly  dead,  some  being  represented  by  rem¬ 
nants  only.  They  were  all  attenuated  and  none  had  produced  flower-stalks. 
Andropogon  nutans,  A.  scoparius,  B.  racemosa,  Spartina,  and  Stipa  had  all 
made  excellent  growth,  but  none  produced  flowers.  Bulbilis,  Elymus,  Poa, 
and  Panicum  also  grew  well  and  blossomed  about  normally. 

The  sods  in  the  Poa  zone,  which  were  planted  at  the  same  time,  made  a 
good  growth  early  in  the  season.  By  the  end  of  June,  Spartina,  Cyperus, 
Mentha,  etc.,  had  reached  a  level  of  about  3  feet  and  the  shade  was  dense. 
Bulbilis  and  Bouteloua  gracilis  both  had  delicate  slender  leaves  10  to  14  inches 
tall,  while  those  of  Koeleria  reached  15  inches.  None  had  blossomed,  but 
Stipa  had  a  few  fruits  which  were  smaller  than  normal.  On  August  31,  one- 
half  of  Bouteloua  gracilis  was  dead  and  Distichlis  was  nearly  so.  However, 
most  of  the  other  species,  though  slender,  had  made  in  almost  every  case  a 
much  better  growth  than  in  the  wetter  part  of  the  swamp.  Six  of  the  13 
species,  viz,  Andropogon  scoparius,  A.  nutans,  Stipa,  Distichlis,  Elymus,  and 
Panicum,  blossomed,  in  contrast  to  4  of  the  14  species  in  the  swamp. 

In  1922,  the  swamp  area  was  much  drier  than  during  preceding  years;  in 
fact  there  was  nowhere  excess  holard  or  deficient  aeration,  light  being  the 
controlling  factor.  Spartina  was  over  2.5  feet  tall  by  the  middle  of  June 
and  4  feet  in  August,  covering  the  area  with  a  dense  growth.  Conditions 
were  very  similar  in  the  Poa  zone.  The  leaves  on  practically  all  of  the  plants 
were  very  narrow,  long,  and  delicate,  Andropogon  scoparius  did  not  appear 
in  the  spring,  and  Koeleria  died  in  August.  The  following  early  bloomers 
produced  flowers:  Bulbilis,  Koeleria,  Stipa,  and  Poa,  while  the  subclimax 
dominants  Elymus  and  Panicum  also  blossomed.  By  June  of  1923,  Boute¬ 
loua  hirsuta,  Bulbilis,  and  Distichlis  were  dead,  while  Bouteloua  gracilis,  B. 
racemosa,  Elymus,  and  Stipa  vanished  later  in  the  summer.  This  left  a  few 
remnants  of  Agropyrum  and  well-developed  plants  of  Andropogon  nutans, 
Panicum  virgatum,  and  Spartina  cynosuroides  at  the  end  of  the  third  season. 
In  the  Poa  zone  all  survived  the  1922  season,  but  the  following  species  died 
the  next  summer:  Andropogon  nutans,  A.  scoparius,  Bulbilis,  Bouteloua 
gracilis,  Distichlis,  and  Elymus.  Agropyrum,,  Bouteloua  racemosa,  and  Stipa 
spartea  were  represented  by  remnants  only,  while  Andropogon  fur catus,  Pani¬ 
cum,  and  Spartina  were  the  only  species  that  had  developed  normally. 

The  fate  of  the  sods  planted  in  the  swamp  during  1920  is  instructive.  A. 
scoparius,  A.  fur  catus,  A.  nutans,  B.  gracilis,  B.  racemosa,  Koeleria,  and  Stipa 
died  the  first  season,  while  many  of  the  others  came  through  in  very  poor 
condition  (table  69).  In  May  of  the  following  spring  Agropyrum  and  Elymus, 
and  especially  Poa,  showed  signs  of  distress.  Spartina  developed  nor¬ 
mally,  while  Panicum  and  Distichlis  were  in  good  health.  Both  Agropyrum 
and  Poa  had  died  by  the  end  of  July;  autumn  found  remnants  only  of  Distich¬ 
lis  and  Elymus,  but  Panicum  and  Spartina  had  made  a  good  growth  and 
seeded.  During  1920,  Koeleria,  Stipa,  Andropogon  scoparius,  and  A.  nutans 


88 


EXPERIMENTS  DURING  1921. 


died  in  the  Poa  zone.  The  following  spring  Agropyrum  glaucum  and  Bouieloua 
racemosa  failed  to  appear,  while  B.  gracilis  died  in  June  after  a  feeble 
growth.  Distichlis  succumbed  in  August,  but  Elymus ,  Poa,  Panicum ,  and 
Sparlina  made  a  fairly  normal  growth,  all  ripening  seed. 

Since  the  swamp  was  much  drier  and  the  air-content  higher,  the  chief 
factor  inhibiting  growth  was  not  aeration  but  light  (p.  73).  Spartina  be¬ 
came  indistinguishable  from  the  surrounding  vegetation.  Panicum,  blos¬ 
somed  normally,  Elymus  bore  a  single  flower-stalk  2  feet  high,  while  Distichlis 
did  very  poorly.  In  the  Poa  zone,  Poa  and  Elymus  made  an  excellent  growth, 
the  former  merging  into  the  common  sod  and  the  latter  flowering  at  a  height 
of  over  4  feet.  Panicum  and  Spartina  developed  normally  in  every  way. 
In  1923  Distichlis  died,  but  the  three  low-prairie  species  developed  very  well, 
the  4  species  in  the  Poa  zone  also  prospering.  The  results  are  in  accord  with 
the  expectation,  since  all  the  species  except  those  of  the  mesophytic  subclimax 
prairie,  viz,  Andropogon  furcatus,  Elymus,  Panicum,  and  Spartina,  had  lost 
in  the  struggle  during  the  period  of  3  or  4  years. 

Regional  Transplants. 

As  to  the  fate  of  the  sods  transplanted  to  Colorado  Springs  in  1920,  both 
blocks  of  Stipa  spartea  had  died  by  the  end  of  1921,  as  well  as  one  each  of  the 
following  species:  Andropogon  furcatus,  A.  scoparius,  Bouieloua  racemosa , 
Elymus,  Koeleria,  and  Panicum.  This  was  chiefly  due  to  drought,  but  partly 
also  to  overgrazing,  stock  having  broken  into  the  inclosure  at  several  times. 
In  1922,  Bulbilis  alone  blossomed,  repeated  grazing  again  weakening  the  other 
plants.  By  the  autumn  of  1923,  grazing  having  been  continued,  the  last  lot 
of  Elymus  had  died,  several  of  the  other  species  were  represented  by  rem¬ 
nants  only,  and  all  were  in  rather  poor  condition. 

During  1921,  sods  of  Stipa  setigera,  S.  eminens,  Poa  tenuifolia,  and  Melica 
imperfecta  from  California  were  transplanted  into  high  and  low  prairie  re¬ 
spectively  on  June  23.  These  were  received  at  Lincoln  on  May  18,  but  were 
kept  in  a  garden  and  watered  frequently  before  the  large  blocks  of  soil  con¬ 
taining  the  transplant  were  removed  to  the  native  grassland.  Here  they  were 
again  watered  from  time  to  time  as  necessary.  Only  a  few  made  a  feeble  growth 
and  all  on  the  high  prairie  were  dead  by  July  30.  On  the  low  prairie  four  lots 
put  out  new  shoots  3  to  5  inches  long,  but  these  died  by  the  end  of  the  summer. 

On  July  20  the  following  species  from  Arizona  were  transplanted  in  quad¬ 
ruplicate  into  a  garden  at  Lincoln  and  kept  well  watered :  Bouteloua  eriopoda, 
B.  rothrocki,  B.  bromoides,  and  Aristida  divaricata.  All  made  some  growth.  In 
September  one  clump  of  B.  eriopoda  bore  flower-stalks  about  15  inches  tall, 
and  one  B.  bromoides  possessed  leaves  9  inches  high  and  flowered  abundantly 
at  15  to  22  inches. 


4.  EXPERIMENTS  DURING  1922. 

PHYSICAL  FACTORS. 

Rainfall. 

The  season  of  1922  was  fairly  favorable  for  growth,  except  the  latter  part, 
when  severe  drought  occurred  at  all  the  stations,  being  relatively  less  marked 
at  Burlington.  At  Lincoln  the  combined  precipitation  for  March  and  April 
averaged  about  normal;  that  of  May  and  June  was  approximately  1  and  2 
inches  below  the  mean  respectively,  July  had  an  excess  of  2.4  inches,  but  only 
0.7  of  the  3.7  normal  rainfall  of  August  occurred  (fig.  9).  At  Phillipsburg  the 
April  precipitation  was  nearly  1.5  inches  above  normal  (no  report  for  May), 
June,  July,  August,  and  September  showing  deficiencies  of  2.4,  0.6,  1.8,  and 
1.6  inches  respectively  (fig.  15).  The  Burlington  precipitation  was  about 
half  the  normal  during  March  (April  report  missing),  0.4  inch  in  excess  during 
May,  while  June  gave  an  excess  of  1.4  inches  over  the  mean.  July  had  a 
deficiency  of  0.8,  August  an  excess  of  0.5,  and  September  was  also  far  below 
the  normal  (fig.  16).  Spring  and  early  summer  drought  periods,  i.  e.,  rainfall 
less  than  0.21  inch,  occurred  at  Lincoln  from  April  11  to  May  8  and  May  26 
to  June  24.  At  Phillipsburg  a  10-day  drought  occurred  in  April  (May  report 
missing)  and  no  rain  fell  from  June  1  to  26.  The  severity  of  the  late-summer 
drought  at  both  Lincoln  and  Phillipsburg  is  well  illustrated  by  the  fact  that 
by  the  end  of  August  the  late-developing  A ndropogons  were  already  half  dried 
and  appeared  to  be  entering  the  winter  condition.  No  efficient  precipitation 
fell  at  Burlington  from  May  2  to  19  and  20  to  29  (April  report  missing)  or 
June  2  to  15. 

Holard. 

A  study  of  the  water-content  (table  31)  shows  that  a  margin  of  5  per  cent 
(more  usually  7  to  1 1  per  cent)  above  the  hygroscopic  coefficient  existed  at  all 
times  to  a  depth  of  4  feet  in  the  high  prairie  at  Lincoln  (except  in  the  surface 
6  inches  on  June  22). 

At  the  mixed-prairie  station  a  good  water-content  prevailed  to  3  feet  in  the 
spring,  but  the  margin  of  safety  was  much  less  at  nearly  every  determination 
than  at  Lincoln.  Late  in  June,  and  again  throughout  July  and  August, 
drought  prevailed,  no  water  being  available  often  to  depths  of  4  feet.  Condi¬ 
tions  at  Burlington  were  not  very  different,  the  soil  in  spring  and  early  summer 
being  as  usual  quite  moist.  However,  the  deficiencies  were  very  marked  and 
practically  continuous  after  June  18. 

Temperature. 

Air-temperatures  in  general  were  lowest  at  Burlington,  7°  F.  higher  at 
Lincoln  during  early  May,  and  usually  3  to  5°  higher  during  the  rest  of  the 
season;  those  at  Phillipsburg  exceeded  those  at  Lincoln  by  2  to  5°,  especially 
after  June  7  (fig.  38).  The  night  temperatures  at  Burlington  were  decidedly 
lowest  (by  2  to  10°),  those  at  Lincoln  intermediate,  and  at  Phillipsburg 
highest  (fig.  39).  A  similar  general  relation,  but  one  less  marked  and  with 
overlappings,  holds  for  the  day  temperatures.  Soil-temperatures  at  a  depth 
of  3  inches  were  obtained  until  the  middle  of  June,  after  which  the  thermo¬ 
graph  bulbs  were  buried  at  a  depth  of  12  inches  and  left  for  the  remainder  of 


89 


90 


EXPERIMENTS  DURING  1922. 


the  season.  In  figure  40  it  may  be  seen  that  the  moister  soil  at  Lincoln  was 
also  that  with  the  lowest  temperature,  although  the  differences,  as  in  the  case 


Table  31. — Holard  in  excess  of  the  hygroscopic  coefficient  at  the  several 

stations,  1922. 

Lincoln,  Nebraska. 


Date. 

0  to  0.5 

0.5  to  1 

1  to  2 

2  to  3 

3  to  4 

foot. 

foot. 

feet. 

feet. 

feet. 

Apr.  30 . 

15.3 

15.8 

14.7 

10.9 

9.1 

May  10 . 

10.1 

13.7 

15.3 

.  .  .  . 

.... 

May  17 . 

12.0 

13.1 

14.1 

12.1 

7.8 

June  7 . 

6.4 

11.2 

10.9 

.  .  .  . 

.  .  .  . 

June  14 . 

6.8 

11.3 

10.5 

8.4 

6.6 

June  22 . 

3.5 

6.3 

11.1 

.... 

.... 

July  6 . 

5.7 

4.7 

8.9 

8.0 

5.4 

July  13 . 

17.8 

11.7 

8.1 

.  .  ,  . 

,  .  .  . 

July  20 . 

16.4 

10.7 

6.2 

.... 

.... 

July  27 . 

21.2 

14.7 

7.5 

.  ,  .  . 

.  •  •  • 

Aug.  3 . 

8.2 

10.1 

7.4 

8.0 

6.0 

Aug.  10 . 

5.6 

6.2 

7.4 

.... 

.  .  .  . 

Aug.  17 . 

0.9 

1.8 

0.8 

.  .  .  , 

.... 

Aug.  24 . 

3.2 

5.4 

5.1 

7.1 

5.3 

Hygroscopic  coeff .... 

9.8 

10.9 

10.1 

10.0 

10.3 

Phillipsburg,  Kansas. 

Apr.  28 . 

18.8 

19.4 

14.1 

1.5 

1.3 

May  19 . 

5.4 

10.2 

9.3 

6.2 

0.4 

June  11 . 

1.7 

9.5 

7.8 

8.2 

0.5 

June  17 . 

1.4 

4.4 

.... 

.... 

.  .  .  . 

June  24 . 

-1.6 

0.9 

.... 

.... 

.  .  .  . 

June  30 . 

10.8 

1.1 

3.7 

5.1 

4.7 

July  17 . 

-1.7 

0.2 

-0.5 

-0.2 

0.9 

July  28 . 

-0.1 

1.6 

,  .  .  . 

.  .  .  . 

.  .  ,  . 

Aug.  3 . 

0.5 

0.7 

-0.5 

-0.1 

0.0 

Aug.  11 . 

-1.5 

-1.8 

-1.3 

.... 

.  .  .  . 

Aug.  17 . 

-3.7 

-1.5 

.... 

.  ,  .  . 

.  .  ,  . 

Aug.  27 . 

-2.6 

-1.4 

0.7 

-1.7 

0.2 

Hygroscopic  coeff .... 

10.6 

10.6 

10.9 

10.6 

10.7 

Burlington,  Colorado. 

Apr.  30 . 

17.6 

16.9 

8.5 

-1.0 

-1.0 

May  20 . 

19.8 

9.6 

8.7 

6.8 

-0.4 

June  4 . 

12.2 

10.3 

8.3 

6.8 

.  .  .  . 

June  11 . 

-0.1 

1.2 

4.5 

4.9 

-1.1 

June  18 . 

0.4 

1.1 

3.8 

.... 

.... 

June  25 . 

0.2 

0.0 

1.2 

2.1 

-0.2 

July  2 . 

11.1 

-1.8 

-2.6 

-0.6 

-1.3 

July  16 . 

-2.5 

-1.9 

-0.5 

0.0 

-1.0 

July  23 . 

6.7 

-1.1 

-0.1 

1.1 

.  .  .  . 

July  30 . 

-0.7 

-0.7 

-0.2 

.  .  .  . 

.  .  .  . 

Aug.  4 . 

5.4 

-1.5 

-1.9 

-0.4 

0.6 

Aug.  20 . 

-1.7 

-1.9 

-1.1 

-0.2 

.  .  .  . 

Aug.  26 . 

-0.3 

-2.1 

-2.7 

-1.9 

-0.4 

Hygroscopic  coeff .... 

10.9 

10.9 

12.2 

12.0 

11.4 

of  air-temperatures,  are  not  great  enough  to  be  of  much  importance  in  the 
establishment  and  growth  of  native  vegetation. 


PHYSICAL  FACTORS. 


91 


Humidity. 

Continuous  records  of  humidity  were  not  obtained  during  1922,  but  a 
comparison  of  the  hygrograph  records  from  Burlington  and  Lincoln,  from 
which  the  average  day  and  average  night  humidities  have  been  obtained, 
shows  striking  differences.  With  few  exceptions,  the  air  at  the  former  was 


Fig.  38. — Average  daily  temperatures  at  Lincoln  (solid  line),  Phillipsburg  (long  broken  lines),  and 

Burlington  (short  broken  lines),  1922. 


13  to  25  per  cent  drier  by  day  (table  32).  Owing  to  the  high  altitude  (4,160 
feet)  and  cool  nights  at  Burlington,  differences  in  night  humidites  were  less 
marked.  Frequent  isolated  readings  at  Phillipsburg,  when  compared  with  the 
records  at  the  other  stations,  showed  that  they  were  usually  intermediate. 

Table  32. — Average  day  and  night  humidites  at  Lincoln  and  Burlington,  1922. 


Date 

Average  day  humidities. 

Average  night  humidities. 

Lincoln. 

Burlington. 

Lincoln. 

Burlington. 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

May  1  to  7 . 

44.7 

45.5 

73.5 

77.3 

8  14 . 

50.5 

26.2 

77.5 

58.2 

15  21 . 

44.5 

39.7 

70.9 

74.5 

22  28 . 

77.4 

64.5 

89.0 

87.9 

29  to  June  4 . 

64.2 

•  •  •  • 

90.2 

•  .  »  • 

June  5  to  11 . 

58.3 

45.8 

87.5 

75.4 

12  18 . 

60.6 

40.5 

86.6 

74.2 

19  25 . 

48.8 

37.2 

73.2 

73.0 

26  to  July  2 . 

61.4 

•  •  •  • 

85.3 

•  •  •  • 

July  3  to  9 . 

60.8 

51.0 

78.5 

82.2 

10  16 . 

71.0 

•  •  •  • 

93.0 

•  •  •  • 

17  23 . 

70.6 

44.5 

89.4 

78.5 

24  30 . 

72.2 

46.1 

92.3 

78.3 

31  to  Aug.  6 . 

66.0 

.... 

90.2 

•  .  .  • 

Aug.  7  to  13 . 

55.3 

61.0 

85.3 

90.6 

14  20 . 

54.0 

42.8 

81.0 

62.1 

21  27 . 

50.2 

•  •  •  • 

80.0 

•  •  •  • 

28  30 . 

56.3 

.... 

87.8 

.... 

92 


EXPERIMENTS  DURING  1922. 


Evaporation. 

The  average  daily  evaporation  (fig.  41)  shows  again  the  relative  xerophytism 
of  the  several  communities,  as  well  as  the  periods  of  stress  in  June  and  August, 
although  that  at  the  two  western  stations  remained  rather  high  throughout 
the  growing-season.  The  evaporation  at  Lincoln  ranged  from  9  to  33  c.  c.,  at 
Phillipsburg  8  to  41  c.  c.,  and  at  Burlington  from  15  to  47  c.  c.  In  general, 
the  losses  were  higher  than  for  the  preceding  year  (fig.  23). 


Fig.  39. — Average  day  (heavy  lines)  and  night  temperatures  (light  lines),  at  Lincoln  (solid  line),  Phil¬ 
lipsburg  (long  broken  lines)  and  Burlington  (short  broken  lines),  1922. 


To  summarize,  the  season  of  1922  was  less  favorable  for  growth  than  1921, 
and  deficiencies  in  rainfall  and  soil  moisture  were  marked,  being  pronounced 
even  at  Lincoln,  the  least  xerophytic  of  the  stations,  during  late  summer. 
Humidity  and  holard  were  again  the  controlling  factors  in  plant  growth, 
conditions  as  regards  both  being  progressively  more  severe  westward. 

PLANTING  RESULTS. 

Surface  Sowing. 

Twenty-two  species  of  grasses,  forbs,  and  trees  were  planted  on  the  sur¬ 
face  of  the  high  prairie  at  Lincoln  on  April  18;  82  per  cent  of  the  species  ger¬ 
minated,  only  Aster  muitiflorus,  Bouteloua  gracilis ,  Solidago  missouriensis,  and 
Sporobolus  asper  failing  to  do  so.  However,  germination  was  considerably 
delayed  because  of  dry  weather.  All  of  the  species  did  at  least  fairly  well 
until  July,  Lespedeza,  Liatris  spp.,  Onagra,  and  Pinus  having  succumbed  by 
the  14th,  while  4  other  species  were  suffering  badly.  The  drought  period, 


SURFACE  AND  TRENCH  SOWING. 


93 


May  26  to  June  24,  was  quite  severe.  During  the  latter  part  the  long-establish¬ 
ed  native  grasses  on  the  high  prairie  had  rolled  leaves  and  Erigeron  ramosus 
was  drying,  many  without  flowering.  It  seems  probable  that  most,  if  not  all,  of 
the  surface-sown  species  would  have  succumbed  except  for  regular  watering. 
Late  August  found  Bouteloua  hirsuta,  Kuhnia,  Ratibida,  and  Robinia  added  to 
the  mortality  list.  Thus,  the  mortality  during  the  first  summer  was  50  per 
cent,  notwithstanding  regular  watering  at  critical  periods  throughout  the 
season.  Liatris  scariosa  died  in  August  1922,  and  Bouteloua  hirsuta  did 
very  poorly,  but  the  5  remaining  species  flourished,  except  during  the  late- 
summer  drought,  Aristida  purpurea,  Bouteloua  racemosa,  and  Elymus  cana¬ 
densis  producing  seed.  Andropogon  nutans,  Bouteloua  hirsuta,  and  Bouteloua 
racemosa  died  during  the  dry  fall  and  winter.  During  the  wet  summer  of  1923 
the  shade  was  very  dense.  At  the  end  of  the  season  Elymus  canadensis  was 
represented  by  a  single  weak  plant ;  Liatris  punctata,  which  was  growing  in  a 
dense  sod,  was  over  a  foot  tall,  but  failed  to  blossom;  but  Aristida  purpurea, 


Fig.  40. — Average  daily  soil  temperatures  at  depths  of  3  and  12  inches  respectively 
at  Lincoln  (solid  line),  Phillipsburg  (long  broken  lines),  and  Burlington  (short 
broken  lines),  1922. 


the  other  survivor,  developed  normally  and  produced  an  abundance  of  seed. 
It  seemed  only  a  question  of  a  year  or  two  more,  however,  until  all  three  would 
disappear  from  the  stabilized  grassland. 


Trench  Sowing. 

Twenty-three  of  the  same  species  sown  on  the  surface  were  also  planted  in  a 
trench  on  the  high  prairie  at  Lincoln  on  April  18.  Seven,  viz,  Amorpha  can- 
escens,  Aster  multi fiorus,  Bouteloua  hirsuta,  B.  gracilis,  Onagra  biennis,  Rati¬ 
bida  columnaris,  and  Solidago  missouriensis,  failed  to  germinate.  Of  the  70 
per  cent  germinating,  Agropyrum  glaucum  and  Liatris  punctata  died  before  the 
end  of  the  June  drought  and  many  others  wilted  badly.  Lespedeza  capitata, 
Muhlenbergia  pungens,  Petalostemon  candidus,  and  Sporobolus  asper  succumbed 
by  the  middle  of  July,  while  the  remaining  ten  species  (63  per  cent)  lived 
throughout  the  summer.  Most  of  them,  however,  were  in  poor  condition, 
being  badly  dried  by  August  21. 


94 


EXPERIMENTS  DURING  1922. 


Plants  in  the  trench  at  Phillipsburg  did  much  more  poorly.  Of  the  23 
species  planted  on  April  29  only  8  (35  per  cent)  germinated.  One-half  of  the 
trench  was  rather  densely  shaded  by  Bouteloua  racemosa  and  Andropogon 
furcatus,  and  germination  in  it  was  very  low.  Only  about  hah  of  those  that 
germinated  did  so  abundantly.  Liatris  scariosa  and  Sporobolus  asper  died 
by  June  30,  and  Agropyrum  glaucum  in  July,  while  Elymus  canadensis,  Des- 
modium  canescens,  and  Kuhnia  glulinosa  succumbed  in  August.  Andropogon 
nutans  and  Bouteloua  racemosa  were  the  only  ones  that  survived  the  first 
summer.  Although  the  prairie  had  been  burned  over  the  preceding  winter 
through  accident,  by  May  27  the  general  level  of  the  grasses  had  reached  5 
or  6  inches,  while  an  upper  story  of  Psoralea,  Helianthus,  Erigeron,  and  flower- 
stalks  of  Boa  and  Siipa  at  15  to  22  inches  added  to  the  shade.  Consequently, 
light  early  became  an  important  factor. 

c.c 

40 

30 


20 


10 


0 

Fig.  41. — Average  daily  evaporation  at  Lincoln  (solid  line),  Phillipsburg  (long 
broken  lines),  and  Burlington  (short  broken  lines),  1922. 

Twenty-two  species  were  sown  on  the  surface  of  the  mixed  prairie  at  Phil¬ 
lipsburg  on  April  29,  the  spring  being  late  at  all  stations.  Of  these,  14  per 
cent,  including  Aster  multiflorus,  Lespedeza  capitata,  and  Solidago  missouri - 
ensis,  failed  to  germinate.  By  June  30  (no  efficient  rain  having  fallen  dur¬ 
ing  June  1  to  26),  4  forbs,  Pinus,  and  Sporobolus  had  succumbed.  On 
August  3,  Agropyrum  was  found  dead,  and  by  the  last  of  the  month 
Amorpha,  Aristida,  Petalostemon,  and  Ratibida  had  also  succumbed.  This 
left  8  species  (42  per  cent)  surviving,  of  which  at  least  4  were  in  very  poor 
condition.  Shading  was  an  important  factor.  As  early  as  June  30  the  grass- 
level  was  8  to  14  inches  high,  with  subdominant  herbs  such  as  Psoralea  at  a 
level  of  24  inches. 

Twenty  of  the  same  species  grown  at  Lincoln  and  Phillipsburg  were  also 
sown  on  the  surface  of  the  short-grass  sod  at  Burlington  on  April  30.  Ten 
species  (50  per  cent)  failed  of  germination.  In  fact,  only  Andropogon  nutans, 
Robinia  pseudacacia,  Desmodium  canescens ,  and  Liatris  scariosa  germinated 
at  all  abundantly.  Some  species  lay  dormant  until  late  in  June,  being 
stimulated  to  grow  by  a  heavy  shower.  By  the  middle  of  July  only  one 
plant  of  Liatris  scariosa  remained  alive,  and  it  succumbed  later.  The  follow¬ 
ing  species  alone  survived  in  both  the  true  and  mixed  prairies:  Andropogon 
furcatus,  A.  nutans,  Bouteloua  racemosa,  Desmodium  canescens,  and  Elymus 


DENUDED  QUADRATS. 


95 


canadensis.  Shading  played  a  minor  role  at  Burlington,  except  in  protecting 
the  plants  from  too  rapid  water-loss,  since  the  short-grass  sod  was  only  3 
inches  tall  by  July  1.  The  fate  of  the  surface  sowing  of  1921  is  of  interest 
here.  At  Lincoln  9  per  cent  survived,  but  none  at  Burlington,  while,  owing 
to  opportune  showers  and  to  a  much  more  favorable  light  relation  at  Phillips- 
burg  than  at  Lincoln,  83  per  cent  survived  the  first  season.  Establishment 
and  growth  in  the  mixed  prairie,  however,  were  better  than  on  the  short- 
grass  plains.  Among  22  species  planted  in  the  trench  at  Burlington  on  April 
30,  68  per  cent  failed  of  germination.  However,  5  of  the  6  species  that  grew 
germinated  rather  abundantly.  Robinia  pseudacacia ,  Desmodium  canescens , 
and  Kuhnia  glutinosa  died  by  the  middle  of  July,  and  Agropyrum  glaucum 
in  August,  while  5  plants  of  Andropogon  nutans  alone  survived  the  summer. 
Andropogon  nutans  was  the  only  species  that  survived  at  all  three  stations, 
reaching  a  height  of  1  to  3  inches  at  Burlington,  5  to  8  inches  at  Phillipsburg, 
and  5  to  9  inches  at  Lincoln.  Bouteloua  racemosa  survived  at  Phillipsburg 
and  Lincoln,  and  8  other  species  at  Lincoln  alone. 

As  to  the  1921  trench  plantings,  the  best  results  were  obtained  at  Lincoln, 
where  5  of  the  11  species  that  germinated  survived  the  first  season. 
Bouteloua  gracilis  died  the  following  June,  but  the  rest  made  fair  to  good 
growth.  During  the  favorable  season  of  1923  growth  was  excellent, 
Andropogon  nutans  and  Sporobolus  asper  reaching  heights  of  8  to  10  inches, 
while  Bouteloua  hirsuta  and  Liairis  scariosa  were  5  to  7  inches  tall,  but  none 
flowered. 

Of  the  6  species  that  started  growth  at  Phillipsburg,  only  Andropogon 
nutans  and  Aristida  purpurea  became  permanently  established.  Both  did 
quite  well  during  1922,  but  Andropogon ,  which  was  densely  shaded,  died  in 
late  summer.  Aristida  was  represented  in  1923  by  a  small  clump  which 
blossomed  profusely  at  a  height  of  22  inches.  No  species  planted  in  the 
trench  in  1921  survived  at  Burlington. 

Denuded  Quadkats. 

Thirty-five  species  of  grasses,  forbs,  shrubs,  and  trees  were  planted  in 
denuded  quadrats  in  the  true  prairie  on  April  18.  Among  these,  ten  (29 
per  cent)  failed  to  germinate.  Brauneria  pallida  died  early  in  June  and 
Acer  negundo  before  the  June  drought  was  broken.  During  this  period 
many  other  species  were  wilted  or  drying.  By  the  middle  of  July,  Agropyrum, 
Elymus,  and  Ulmus  had  also  died,  while  Andropogon  halli  and  Calamovilfa 
longifolia  were  added  to  the  mortality  list  by  August  22.  However,  18  spe¬ 
cies  or  72  per  cent  survived  the  first  summer,  the  list  including  trees  and 
forbs  as  well  as  grasses.  Many  of  these  were  seriously  affected  by  drought. 

Of  32  species  planted  on  April  29  in  denuded  quadrats  in  the  mixed  prairie, 
10  (31  per  cent)  failed  of  germination.  By  June  10,  Lespedeza  and 
Liatris  scariosa  had  died,  and  Agropyrum ,  Muhlenbergia,  and  Ulmus 
disappeared  by  the  end  of  the  month.  Robinia  dried  out  during  July  and 
Acer  negundo  early  in  August.  The  end  of  August  found  Desmodium ,  Elymus , 
Onagra,  and  Pinus  added  to  the  list  of  non-survivors.  This  left  11  species, 
50  per  cent  of  those  which  germinated,  that  survived  the  first  summer.  As 
usual,  most  of  these  showed  by  dead  leaf-tips,  rolled  leaf -blades,  or  browning, 
the  effects  of  intermittent  periods  of  drought. 


96 


EXPERIMENTS  DURING  1922. 


Twenty-eight  species  were  sown  in  denuded  quadrats  at  Burlington 
on  April  30;  50  per  cent  of  them  failed  of  germination.  Among  these 

were  Amorpha,  Aster ,  Liatris,  Ratibida,  Redfieldia,  and  Solidago,  all  of 
which  had  also  failed  at  Lincoln  and  Phillipsburg,  notwithstanding  they 
showed  fair  to  good  germination  in  the  greenhouse  as  well  as  under  other 
methods  of  planting.  Seeds  of  certain  species  kept  on  germinating  until 
July.  By  this  time  Acer  saccharinum  and  Andropogon  furcatus  had  died,  but 
no  further  losses  were  recorded  until  August,  when  Agropyrum  and  Robinia 
also  succumbed.  In  fact,  except  for  the  death  of  Aristida,  no  further  loss 
of  an  entire  species  occurred,  although  many  plants  were  eaten  off  by  grass¬ 
hoppers,  badly  wilted,  or  entirely  destroyed  by  drought.  Thus,  64  per  cent 
survived,  showing  at  once  the  better  conditions  furnished  by  this  method  as 
compared  with  that  of  surface  or  trench  sowing.  The  surface  of  the  soil  in 
these  quadrats,  as  was  true  of  those  2  or  3  years  older,  was  always  mellow; 
Bulbilis  had  started  to  invade  the  older  ones  from  all  sides,  but  the  invasion 
was  very  incomplete,  even  on  areas  denuded  for  over  2  years.  While  the 
grama  in  the  buffalo-grass  sod  was  flowering  rather  sparsely  at  6  to  12  inches, 
that  around  the  edges  of  the  quadrats,  owing  to  an  increased  holard  due  to 
lessened  competition,  was  6  to  20  inches  tall. 

Summary. 

Andropogon  nutans,  Bouteloua  gracilis,  Bouteloua  racemosa,  Gleditsia  tria¬ 
canthus,  Kuhnia  glutinosa,  and  Panicum  virgatum  grew  throughout  the  sum¬ 
mer  at  all  three  stations.  The  following  survived  the  summer  at  two:  Des- 
modium  canescens,  Muhlenbergia  pungens  (Burlington  and  Lincoln),  and  Acer 
saccharinum,  Andropogon  furcatus,  Aristida  purpurea,  Petalostemon  candidus, 
and  Sporobolus  asper  (Phillipsburg  and  Lincoln).  Andropogon  scoparius, 
Liatris  punctata,  Onagra  biennis,  Pinus  ponderosa,  and  Robinia  pseudacacia 
survived  only  at  Lincoln. 

A  comparison  of  the  results  shows  that  Bouteloua  gracilis  made  the  best 
growth  at  Burlington  (5  to  13  inches)  and  the  poorest  at  Lincoln  (2 
to  5  inches).  Gleditsia  grew  poorest  at  Burlington  (2  to  5  inches) 
and  about  the  same  at  the  other  stations  (3  to  7  inches).  However, 
all  of  the  others,  Andropogon  nutans,  Bouteloua  racemosa,  Kuhnia  glutinosa, 
and  Panicum  virgatum,  showed  the  best  growth  at  Lincoln  (4  to  12  inches), 
intermediate  at  Phillipsburg  (3  to  9  inches),  and  least  at  Burlington  (1  to 
5  inches). 

The  fate  of  the  species  planted  in  quadrats  in  1921  is  of  interest  here.  At 
Lincoln,  13  of  the  20  species  that  germinated  survived  the  first  season,  but 
the  following  spring  7  of  these  failed  to  come  up.  The  6  remaining 
species  did  very  well  throughout  the  next  summer,  but  none  came  into  blos¬ 
som.  In  1923,  Andropogon  nutans  formed  a  dense  sod;  Gleditsia  was  repre¬ 
sented  by  a  single  remnant,  and  Stipa  spartea  by  a  scattered  growth.  The 
other  species  did  fairly  well,  but  all  were  much  shaded  and  none  produced 
seed.  At  Phillipsburg,  19  species  germinated  and  13  survived  the  first  sum¬ 
mer;  6  of  these,  including  4  species  of  trees,  were  winterkilled,  and 
Stipa  setigera  died  by  the  end  of  1922.  Agropyrum  and  both  species  of  Sym- 
phoricarpus  did  but  poorly;  Andropogon  nutans  formed  a  dense  sod,  while 
Aristida  and  Elymus  both  ripened  seed.  Of  the  19  species  which  germinated 


SEEDLING  TRANSPLANTS. 


97 


at  Burlington  in  1921,  only  4  survived  the  first  summer.  Gleditsia  was  winter- 
killed  and  Calamovilfa  was  accidentally  destroyed.  Andropogon  nutans  grew 
well  during  both  1922  and  1923  and  reached  a  height  of  6  to  9  inches,  but  Bul- 
bilis  had  invaded  rather  extensively.  Stipa  viridula  died  during  the  severe 
winter  of  1922-23. 

Seedling  Transplants. 

Seedlings  of  20  species  were  transplanted  into  the  high  prairie  on  May 
17  and  watered  freely  from  time  to  time,  as  weather  conditions  demanded, 
until  August  23.  Notwithstanding  this  aid  to  establishment,  Aristida 
purpurea  and  Petalostemon  candidus  died  early  in  June,  Agropyrum 
glaucum  and  Solidago  missouriensis  in  July,  and  Psoralea  tenui flora  flori- 
bunda  and  Stipa  viridula  following  the  drought  in  August.  Several  other 
species  were  represented  by  mere  remnants,  14  (70  per  cent)  surviving  the 
summer.  As  sometimes  happens  under  cultivation,  Onagra  biennis  grew  a 
flower-stalk  the  first  season,  but  failed  to  blossom  and  died  in  the  fall. 

On  May  19,  seedlings  of  19  species  were  transplanted  into  the  mixed  prairie 
at  Phillipsburg.  As  at  the  other  stations,  they  were  about  15  days  old.  In 
planting,  water  was  placed  in  the  bottom  of  the  trench  and  after  it  had  settled 
down,  moist  soil  was  added  around  each  root-mass  until  the  trench  was  two- 
thirds  filled,  wThen  a  second  watering  was  given.  The  trench  was  then  filled 
with  drier  soil  and  finally  covered  with  a  dry  mulch.  At  all  stations  the 
plants  were  watered  for  about  a  week  thereafter.  Agropyrum,  Bouteloua 
racemosa ,  and  Stipa  viridula  died  during  the  June  drought,  and  Psoralea  by 
the  first  of  August,  but  all  the  others  made  a  good  growth,  the  grasses  tillering 
freely  and  Bouteloua  gracilis  and  B.  hirsuta  blossoming.  The  mortality  was 
only  22  per  cent. 

Seedlings  at  Burlington  did  very  poorly.  Of  the  19  species  planted  here  on 
May  20,  only  5  survived,  74  per  cent  succumbing  to  the  unfavorable  condi¬ 
tions  of  the  short-grass  plains;  1  died  early  in  June,  5  more  by  July  2,  7  others 
before  the  first  week  in  August,  and  another  later  in  the  same  month.  On 
August  26,  wilted  or  half-dead  clumps  of  Bouteloua  racemosa,  Stipa  viridula, 
and  Sporobolus  asper,  and  better  lots  of  Bouteloua  hirsuta  and  B.  gracilis, 
2  to  3  inches  tall,  alone  remained.  The  history  was  one  of  repeated  wilting 
and  revival  only  to  wilt  again,  the  conditions  causing  transpiration  at  this 
station  often  being  so  severe  that  vegetation  wilted  even  in  soil  of  good 
water-content.  Under  such  conditions  growth  was  poor.  Only  three  spe¬ 
cies  survived  at  all  the  stations,  viz,  Bouteloua  gracilis,  B.  hirsuta,  and  Sporo¬ 
bolus  asper,  even  under  this  favorable  method  of  transplanting. 

As  to  the  1921  seedlings,  6  of  the  13  species  transplanted  into  high  prairie 
at  Lincoln  died  the  first  summer,  while  2  more  were  winterkilled  (table  61). 
The  5  remaining  species  grew  throughout  1922,  all  surviving  the  drought. 
However,  Andropogon  nutans  and  Stipa  spartea  died  the  following  winter, 
leaving  only  the  three  species  of  Bouteloua.  All  these  made  a  good  growth 
in  1923,  forming  five  clumps  5  to  8  inches  tall. 

At  Phillipsburg,  9  of  the  12  species  survived  the  first  season  and  1  died  the 
following  winter  (table  62).  At  the  end  of  1922  Liatris  scariosa  had  died 
and  Agropyrum  and  Andropogon  nutans  were  doing  very  poorly.  The  rest 
made  a  good  growth,  Bouteloua  hirsuta  alone  producing  flower-stalks.  Andro- 


98 


EXPERIMENTS  DURING  1922. 


yog  on  nutans  and  Agropyrum  died  the  following  winter.  The  two  shorter 
gramas  both  made  a  good  growth  in  1923  and  produced  seed.  Andropogon 
furcatus  was  densely  shaded  and  did  only  fairly  well;  Stipa  spartea  was  repre¬ 
sented  by  a  few  narrow,  densely  shaded  leaves  only,  while  Liatris  punctata 
had  5  fine  plants  about  a  foot  high  that  blossomed  profusely.  None  of  the 
1921  seedlings  at  Burlington  survived  the  first  season. 

Summary. 

The  average  germination  under  all  methods  of  planting  was  similar  to 
that  of  the  two  preceding  years,  Lincoln  being  highest  (74  per  cent),  the  mixed- 
prairie  station  second  (63  per  cent),  and  the  short-grass  plains  last  (44  per 
cent).  However,  as  regards  surface  sowing,  Phillipsburg  ranks  slightly  ahead 
of  Lincoln,  and  this  in  spite  of  frequent  watering  at  the  latter  station.  The 
explanation  for  this  seems  to  lie  in  soil  structure,  that  at  Phillipsburg  being 
much  mellower,  and  hence  it  does  not  crust  when  alternately  wet  and  dry. 


Table  33. — Summary  of  planting  experiments ,  1922. 


Method  of 
planting. 

Per  cent  of  germination. 

Per  cent  of  establishment 
of  germinated  species. 

Lincoln. 

Phillips¬ 

burg. 

Burling¬ 

ton. 

Lincoln. 

Phillips¬ 

burg. 

Burling¬ 

ton. 

Surface  sowing . 

82 

86 

50 

50 

42 

0 

Trench . 

70 

35 

32 

63 

25 

14 

Denuded  quadrats. .  . 

71 

69 

50 

72 

50 

64 

Average . 

74 

63 

44 

62 

39 

26 

Seedlings . 

70 

78 

26 

This  probably  accounts  for  the  8  per  cent  margin  in  favor  of  the  seedling  trans¬ 
plants,  since  in  all  cases  the  percentage  of  germination  falls  off  to  the  west¬ 
ward. 

Sixty-two  per  cent  of  the  species  that  germinated  at  Lincoln  became  estab¬ 
lished,  39  per  cent  at  Phillipsburg,  and  only  26  per  cent  at  Burlington.  The 
same  sequence  held  for  all  methods  of  planting,  except  that  establishment 
in  the  quadrats  at  Burlington  exceeded  by  14  per  cent  that  at  Phillipsburg. 
Both  the  lowest  percentage  of  germination  and  establishment  occurred  in 
the  trench,  the  denuded  quadrats  ranking  highest  in  percentage  of  estab¬ 
lishment. 

Sod  Transplants. 

Large  blocks  of  soil  containing  26  species  of  grasses  and  forbs  were 
transplanted  into  high  prairie  at  Lincoln  March  22  to  April  5.  All  the 
transplants  made  a  good  growth  except  Psoralea  tenuiflora  floribunda,  which 
died  before  the  middle  of  June,  probably  because  of  the  cutting  of  its 
deep  tap-root,  Silphium  integri folium,  which  succumbed  by  the  end  of  August, 
and  Andropogon  scoparius  which  grew  poorly.  In  addition  to  10  of  the 
grasses,  the  following  forbs  blossomed  and  set  seed:  Anemone  cylindrical 
Brauneria  pallida,  Grindelia  squarrosa,  Liatris  scariosa,  Solidago  missouriensis, 
S.  rigida,  and  Vernonia  fasciculata;  only  7  per  cent  of  the  entire  lot  died. 


EDAPHIC  STATIONS. 


99 


Eighteen  blocks  of  sod,  representing  13  species  of  grasses,  were  transplanted 
from  Lincoln  into  the  short-grass  sod  at  Burlington  on  April  15.  Although 
none  died,  the  growth  was  with  few  exceptions  rather  poor,  being 
characterized  by  scattered  shoots,  frequently  with  rolled  leaves  and  dead 
leaf -tips.  Flowers  were  present  in  61  per  cent  as  compared  with  67  per  cent 
of  the  grasses  transplanted  at  Lincoln.  In  all  cases,  however,  the  flower- 
stalks  were  3  to  10  inches  shorter  and  usually  few  in  number,  while  the 
inflorescence  itself  was  dwarfed.  For  example,  Agropyrum  headed  at  Bur¬ 
lington  at  11  inches,  while  at  Lincoln  the  flower-stalks  were  21  to  27  inches 
tall;  Elymus  headed  at  12  to  18  inches  in  the  Great  Plains,  but  in  the  true 
prairie  at  28  inches.  The  vegetative  growth  was  proportionately  dwarfed. 

EXPERIMENTS  AT  OTHER  STATIONS,  1922. 

Physical  Factors. 

Water  Relations. 

Studies  were  continued  during  1922  at  the  series  of  edaphic  stations  at 
Lincoln,  and  at  Nebraska  City  and  Colorado  Springs.  The  general  conditions 
of  precipitation  at  Lincoln  have  already  been  given.  The  season  at  Nebraska 
City  was  one  marked  by  June  and  August  drought.  April  precipitation  was 
nearly  normal,  May  showed  a  deficiency  of  1  inch,  June  of  2.6  inches,  and, 
although  July  had  an  excess  of  3  inches,  August  had  a  rainfall  of  only  0.7 
inch  instead  of  the  normal  3  inches  (fig.  18).  Drought  periods  occurred  on 
April  11  to  30,  May  6  to  20,  May  25  to  June  10,  and  June  11  to  25.  The 
water-content  in  excess  of  the  hygroscopic  coefficient  at  Nebraska  City  and 
Lincoln  low  prairie  is  given  in  table  34,  where  that  of  the  high  prairie  is  added 
for  purposes  of  comparison.  A  study  of  the  table  shows  that  notwithstanding 
the  decreased  rainfall,  the  soil  at  Nebraska  City  usually  had  a  margin  of  at 
least  8  per  cent  chresard  below  the  first  foot  of  soil.  Exceptions  to  this 
occurred  after  the  first  week  in  June  and  again  in  August.  However,  the 
chresard  in  the  surface  foot,  which  most  critically  affects  seedlings,  was 
practically  exhausted  on  June  17,  and  was  very  low  on  August  17,  as  well  as 
at  certain  other  periods.  As  a  whole,  the  holard  was  less  favorable  than 
during  1921. 

Water-content  on  the  low  prairie  was  more  favorable  than  that  at  Nebraska 
City  and  considerably  in  excess  of  that  on  the  high  prairie.  At  no  time  was 
there  a  margin  of  less  than  7  per  cent  available  at  any  level,  and  it  was  usually 
10  to  12  per  cent.  Conditions  on  the  gravel-knoll  were  much  less  favorable 
than  during  the  preceding  year,  as  was  evidenced  by  the  drying  of  the  grama 
grasses  during  a  drought  when  no  water  was  available  in  the  first  2  feet 
of  soil. 

The  average  daily  evaporation  at  Nebraska  City  was  considerably  lower 
than  on  the  high  prairie  at  Lincoln.  During  the  4  months  (last  half  of  May, 
June,  July,  and  August)  the  average  daily  rates  were  as  follows:  12.4  and  15.1, 
18.4  and  29,  12.7  and  13.5,  14.4  and  20.2  c.  c.  respectively.  Isolated  humidity 
readings  taken  from  time  to  time  and  compared  with  the  hygrograph  record 
at  Lincoln  for  the  same  hour  showed  conditions  not  greatly  different  from 
from  those  of  the  preceding  year. 


100 


EXPERIMENTS  DURING  1922 


Table  34. — Holard  in  excess  of  hygroscopic  coefficient  in  1922. 

High  Prairie. 


Date. 

0  to  0.5 
foot. 

0.5  to  1 
foot. 

1  to  2 
feet. 

2  to  3 
feet. 

3  to  4 
feet. 

Apr.  30 . 

15.3 

15.8 

14.7 

10.9 

9.1 

May  10 .  . 

10.1 

13.7 

15.3 

May  17 . 

20.0 

13.1 

14.1 

12.1 

7.8 

June  7 . 

6.4 

11.2 

10.9 

June  14 . 

6.8 

11.3 

10.5 

8.4 

6.6 

June  22 . 

3.5 

6.3 

11.1 

July  6 . 

5.7 

4.7 

8.9 

8.0 

5.4 

July  13 . 

17.8 

11.7 

8.1 

July  20 . 

16.4 

10.7 

6.2 

July  27 . 

21.2 

14.7 

7.5 

Aug.  3 . 

8.2 

10.1 

7.4 

8.0 

6.0 

Aug.  10 . 

5.6 

6.2 

7.4 

Aug.  17 . 

0.9 

1.8 

0.8 

Aug.  24 . 

3.2 

5.4 

5.1 

7.1 

5.3 

Hygroscopic  coeff .... 

9.8 

10.9 

10.1 

10.0 

10.3 

Low  Prairie. 

Apr.  30 . 

18.4 

10.4 

20.6 

12.5 

18.2 

May  17 . 

13.4 

16.1 

17.0 

17.0 

17.6 

May  31 . 

26.7 

21.3 

18.7 

June  7 . 

13.2 

14.6 

15.2 

June  14 . 

10.7 

13.8 

15.1 

13.8 

19.0 

June  22 . 

6.9 

9.4 

15.4 

June  29 . 

21.9 

10.2 

11.0 

July  6 . 

13.4 

8.0 

6.8 

12.8 

16.6 

July  13 . 

28.1 

16.8 

11.5 

July  20 . 

26.3 

21.1 

11 .2 

July  27 . 

30.6 

28.7 

15.3 

Aug.  3 . 

17.5 

14.6 

11.8 

11.1 

15.9 

Aug.  10 . 

10.2 

15.8 

13.7 

Aug.  17 . 

7.9 

9.8 

11.0 

Aug.  24 . 

7.8 

6.8 

11.1 

11.8 

15.9 

Hygroscopic  coeff .... 

10.0 

9.6 

9.2 

11.1 

10.8 

Nebraska  City. 

Apr.  22 . 

17.9 

19.3 

18.3 

15.0 

13.3 

May  13 . 

8.7 

16.2 

17.4 

14.4 

13.2 

May  20 . 

4.4 

11.0 

16.1 

June  3 . 

18.4 

18.8 

17.0 

15.0 

14.3 

June  10 . 

4.3 

9.4 

12.3 

June  17 . 

-0.3 

1.5 

7.9 

11.2 

June  21 . 

2.0 

4.2 

10.4 

10.3 

10.2 

June  28 . 

4.4 

0.8 

5.0 

12.2 

11.8 

July  5 . 

8.5 

0.9 

5.9 

July  12 . 

25.6 

21.6 

17.7 

10.2 

10.3 

July  19 . 

7.6 

13.4 

9.9 

July  26 . 

5.5 

10.3 

9.1 

Aug.  1 . 

18.2 

16.3 

13.1 

9.9 

9.5 

Aug.  8 . 

11.9 

12.7 

10.4 

Aug.  15 . 

1.5 

6.1 

7.8 

Aug.  22 . 

11.2 

7.1 

4.1 

Aug.  31 . 

3.7 

4.8 

6.8 

8.0 

3.4 

Hygroscopic  coeff .... 

12.1 

11.7 

12.3 

13.6 

12.9 

EDAPHIC  STATIONS!  SURFACE  SOWING. 


101 


Planting  Results. 

Surface  Sowing. 

Of  typical  grasses  and  forbs,  19  species  were  sown  on  the  surface  of  the 
low  prairie  on  April  20,  1922;  unlike  the  high  prairie  and  gravel-knoll,  this 
area  had  not  been  burned.  A  dense  tangle  of  grass-leaves  and  flower-stalks 
covered  the  ground  and  formed  a  loose  mulch  to  a  depth  varying  from  2  to  4 
inches.  This  not  only  greatly  affected  the  light  relations,  but  also  the  air  was 
of  much  higher  humidity  and  lower  temperature  below  the  mulch,  and  the 
soil  was  cooler.  For  example,  at  2  p.  m.  on  a  clear  day  (May  28)  an  average 
of  four  thermometer  readings  at  a  depth  of  an  inch  under  the  mulch  gave  a 
temperature  of  68°  F.,  while  that  at  a  similar  depth  in  denuded  quadrats  was 
95°  F. 

Under  these  conditions  the  plants  germinated  slowly,  Desmodium  canescens, 
Liatris  punctata  and  scariosa,  and  Petalostemon  candidus  alone  appearing  above 
ground  by  May  17.  Moreover,  by  May  26  the  new  growth  of  the  dominants 
was  10  to  15  inches  tall,  so  that  light  relations  played  an  exceedingly  important 
role  from  the  first.  However,  only  3  species,  Aster  multiflorus ,  Ratibida  colum- 
naris,  and  Solidago  missouriensis,  failed  to  germinate.  Weak  plants  of 
Amorpha  canescens,  Onagra  biennis,  and  Sporobolus  asper  lasted  only  until  the 
middle  of  June,  and  Kuhnia  glutinosa,  Liatris  scariosa  and  punctata,  and 
Lespedeza  capitata  died  within  the  next  30  days,  all  showing  the  effects  of 
shading.  Bouteloua  hirsuta  succumbed  by  August  and  B.  gracilis,  B.  racemosa, 
Desmodium  canescens,  and  Elymus  canadensis  during  this  month.  This  left 
remnants  of  Aristida  purpurea  and  Andropogon  nutans,  as  well  as  rather  good 
growths  of  Andropogon  furcatus  and  Petalostemon  candidus .  The  total  mor¬ 
tality  was  75  per  cent  during  the  first  summer.  The  severe  competition  for 
light  on  the  low  prairie  was  chiefly  responsible  for  this;  by  June  7  the  surface 
and  trench  plantings  were  already  badly  shaded,  while  by  June  22  the  general 
grass  level  was  18  inches;  by  September  1,  that  of  the  foliage  reached  over  2 
feet  and  the  flower-stalks  43  inches.  In  the  part  of  the  area  unmown  since 
1919,  growth  was  even  greater. 

On  the  surface  at  Nebraska  City,  20  species  were  sown  on  April  22.  Spring 
opened  late  and  the  soil  was  in  excellent  condition  as  regards  holard.  Nine 
species  were  above  ground  by  May  13.  Aster  multiflorus,  Bouteloua  gracilis, 
Lespedeza  capitata,  Onagra  biennis,  Solidago  missouriensis,  and  Sporobolus 
cryptandrus  failed  to  germinate.  By  June  21,  most  of  the  plants  were  badly 
wilted  and  Liatris  scariosa  and  Pinus  ponder osa  had  succumbed.  Robinia 
pseudacacia  died  in  July,  Agropyrum  glaucum  and  Petalostemon  candidus  by 
August,  while  Amorpha  canescens  and  Ratibida  columnaris  were  found  dead 
on  August  31.  Only  50  per  cent  survived.  These  included  slender,  delicate 
specimens  of  Andropogon  nutans,  A.  furcatus,  Bouteloua  hirsuta ,  B.  racemosa, 
Elymus  canadensis,  Kuhnia  glutinosa,  and  Liatris  punctata.  A  similar  lot  of 
seeds  was  sown  on  the  surface  at  Colorado  Springs  on  May  5,  but  these,  like 
those  planted  in  the  trench  and  denuded  quadrats,  showed  no  germination 
when  examined  on  May  25  and  again  on  July  4,  owing  to  unfavorable  holard. 

As  regards  the  1921  surface  sowings,  it  may  be  recalled  that  none  survived, 
owing  to  the  dense  shade.  At  Nebraska  City,  Bouteloua  gracilis  and  B. 
hirsuta  alone  were  represented  by  delicate  seedlings  at  the  end  of  the  first 


102 


EXPERIMENTS  DURING  1922. 


season.  However,  they  held  out  during  the  summer  of  1922,  although  very 
much  attenuated.  During  1922  they  were  still  very  slender  and  delicate,  but 
they  survived  this  third  season  of  growth,  although  densely  shaded,  indicating 
an  unexpectedly  high  tolerance  of  shade  for  the  short-grasses. 

Trench  Sowing. 

Seeds  of  20  species  were  planted  in  a  trench  on  the  low  prairie  on  April  20. 
Amorpha  canescens,  Aster  multiflorus,  Onagra  biennis,  Ratibida  columnaris, 
Sporobolus  asper,  and  Solidago  missouriensis  did  not  germinate.  Nearly  all 
of  the  others  grew  in  considerable  abundance,  except  Bouteloua  hirsuta  and 
Liatris  punctata,  which  were  represented  by  a  few  plants  each,  all  dying  before 
the  end  of  June.  The  others  did  quite  well  during  the  rainy  month  of  July, 
Liatris  scariosa,  Lespedeza  capitata,  and  Muhlenbergia  pungens  disappearing 
by  August.  Nine  species  (64  per  cent  of  those  that  germinated)  became 
permanently  established,  and  although  slender  were  in  fairly  good  condition 
at  the  end  of  the  summer. 

A  similar  lot  of  seeds,  representing  21  species,  was  planted  in  a  trench  in 
subclimax  prairie  on  April  22.  Eight  species,  including  3  which  grew  at 
Lincoln,  failed  of  germination.  Agropyrum  glaucum,  Muhlenbergia  pungens, 
Petalostemon  candidus,  and  Pinus  ponderosa  died  before  June  20,  the  last 
having  been  dug  up  by  rodents.  Andropogon  nutans,  A.  furcatus,  Liatris 
scariosa  and  punctata  died  before  the  middle  of  July,  and  Elymus  canadensis 
in  August.  This  left  a  few  weak  plants  each  of  Bouteloua  racemosa,  Kuhnia 
glutinosa,  and  Robinia  pseudacacia,  but  a  good  sod  of  Andropogon  nutans  7  to 
9  inches  high. 

Of  the  1921  trench  plantings  on  the  low  prairie,  remnants  of  Aristida 
purpurea  alone  survived  the  first  season,  and  these  were  accidentally  destroyed 
the  next  spring  in  transplanting.  At  Nebraska  City,  Andropogon  nutans 
alone  was  alive  the  following  spring.  In  1922  it  reached  a  height  of  13  inches, 
and  did  quite  as  well  the  next  season,  but  it  failed  to  blossom.  On  the  gravel- 
.  knoll,  Andropogon  nutans  alone  survived,  but  although  it  grew  well  early  the 
next  spring,  it  died  the  following  June. 

Denuded  Quadrats. 

On  April  20,  27  species  were  sown  in  denuded  quadrats  on  the  low  prairie. 
Five  did  not  germinate.  These  belonged  to  different  species  from  those 
failing  of  germination  in  the  trench,  and  included  Brauneria  pallida,  Corylus 
americana,  Fraxinus  lanceolata,  Gleditsia  triacanthus,  and  Ratibida  columnaris. 
During  the  June  drought,  Agropyrum,  Aristida,  Aster,  Lespedeza,  Liatris 
punctata,  and  Solidago  succumbed;  Elymus,  Muhlenbergia,  and  Ulmus  also 
died  before  August  1.  This  gave  a  mortality  of  40  per  cent,  though  most  of 
the  survivors  were  in  good  condition  at  the  end  of  the  summer. 

Among  32  species  planted  at  Nebraska  City,  10  did  not  germinate.  Muhl¬ 
enbergia  and  Petalostemon  died  before  June  and  the  following  as  a  result  of 
the  June  drought:  Acer  saccharinum,  Aristida,  Liatris  scariosa  and  punctata, 
Ratibida,  and  Ulmus.  Later,  Agropyrum  and  Lespedeza  were  lost,  giving  a 
total  mortality  of  46  per  cent.  Among  the  survivors  were  4  species  of  trees 
(two  of  which,  Acer  negundo  and  Gleditsia  triacanthus,  were  in  fine  condition), 
2  forbs,  and  6  grasses.  In  general,  they  were  in  good  condition.  By  the 


EDAPHIC  STATIONS!  SEEDLING  TRANSPLANTS. 


103 


end  of  August  the  average  height-level  of  the  grassy  vegetation  was  16 
inches,  shade  being  dense  over  most  of  the  quadrats.  However,  very  little 
invasion  had  occurred. 

As  to  the  denuded  quadrats  planted  in  1921,  10  of  the  12  species  that  grew 
on  the  low  prairie  survived  the  first  summer.  Acer  negundo,  A.  saccharinum, 
and  Lespedeza  capitata  failed  to  grow  the  following  spring,  and  Elymus  died 
in  June,  as  did  also  Bouteloua  gracilis,  perhaps  as  a  result  of  the  surface 
soil  washing  away  from  the  roots.  All  of  the  others  except  Corylus  ameri- 
cana  made  a  good  growth,  the  latter  being  badly  eaten  by  grasshoppers.  All 
were  densely  shaded  and  none  flowered.  Corylus  did  not  survive  the  dry 
fall  and  winter  following,  while  Aristida  died  during  the  summer  of 
1923,  evidently  being  unable  to  longer  endure  the  dense  shade.  At  the  end  of 
the  summer  Sporobolus  was  represented  by  remnants  only.  Symphoricarpus 
made  only  a  fair  growth,  while  Andropogon  nutans  alone  developed  normally, 
reached  a  height  of  25  to  30  inches  and  merged  into  the  native  sod. 

At  Nebraska  City  only  8  of  the  15  species  that  grew  survived  the  first 
summer.  Gleditsia  and  Robinia  failed  to  appear  in  the  spring  of  1922  and 
Calamovilfa  died  early  in  June.  All  of  the  other  species  made  a  good  growth, 
Andropogon  merging  into  the  native  sod.  None  of  the  quadrats  were  much 
invaded.  No  flower-stalks  were  produced  by  any  of  the  plants.  In  1923  the 
6  remaining  species  all  did  quite  well,  several  of  them  seeding  rather  abun¬ 
dantly. 

On  the  gravel-knoll,  40  per  cent  of  the  species  that  grew  survived  the  first 
season.  During  1922  some  of  the  Lespedeza  seeds,  sown  the  preceding 
spring,  germinated,  but  these  and  the  few  feeble  shoots  from  Symphori¬ 
carpus  rhizomes  were  all  dead  by  midsummer.  Aristida  and  Elymus  both 
seeded,  but,  like  Andropogon,  suffered  severely  from  the  August  drought. 
During  the  following  dry  fall  and  winter  Elymus  died,  but  in  1923  both  Aris¬ 
tida  and  Andropogon  made  a  good  growth  and  seeded. 

Seedling  Transplants. 

Seedlings  were  transplanted  both  on  the  low  prairie  and  at  Nebraska  City, 
22  pots  containing  18  species  being  used  in  growing  the  plants  for  each  station. 
The  transplanting  was  done  at  Lincoln  on  May  17.  One  lot  of  Agropyrum 
died  in  June  and  another  in  July,  together  with  Elymus,  Koeleria,  Liatris,  and 
Stipa  spartea;  Ratibida,  Kuhnia,  Argemone,  Onagra,  and  Psoralea  succumbed 
in  August,  making  a  total  loss  of  55  per  cent.  Most  of  the  survivors  came 
through  the  season  in  good  condition,  owing  to  the  adequate  water-content 
even  during  the  August  drought. 

At  Nebraska  City,  Agropyrum,  Koeleria,  Lespedeza,  Solidago,  and  Stipa  viri- 
dula  died  before  the  end  of  June.  Three  others  failed  in  July,  viz,  Aristida, 
Glycyrrhiza,  and  Liatris,  and  August  added  Psoralea  to  the  list,  making  a 
total  of  41  per  cent.  Most  of  the  survivors  grew  well,  Bouteloua  hirsuia 
putting  forth  flower-stalks. 

To  complete  the  history  of  the  1921  seedling  transplants,  only  14  per  cent 
survived  on  the  gravel-knoll,  constituted  by  Bouteloua  hirsuta  and  Andro¬ 
pogon  nutans.  During  1922  these  made  only  a  poor  vegetative  growth,  fre¬ 
quently  wilting,  and  did  not  put  forth  flower-stalks.  By  August  1923  they 
had  reached  a  height  of  8  inches,  neither  coming  into  blossom. 


104 


EXPERIMENTS  DURING  1922. 


On  the  low  prairie  a  single  species  died  the  first  season,  but  by  the  next 
spring  Aristida  purpurea  and  Liatris  scariosa  were  dead  and  Bouteloua  race - 
mosa  was  represented  by  a  single  plant  which  died  in  June.  The  rest 
made  a  fair  to  excellent  growth,  except  Stipa  comata.  The  shade  was 
dense  and  Elymus  canadensis  alone  grew  above  the  general  level  and 
headed  at  35  inches.  No  others  blossomed. 

During  the  summer  of  1923  the  following  species  were  so  deeply  shaded 
that  they  died :  Bouteloua  hirsuta,  B.  gracilis,  Liatris  punctata,  Stipa  viridula, 
and  S.  comata.  Elymus  headed  at  about  3  feet  and  Stipa  spartea  seeded  at 
2  feet,  but  neither  Andropogon  nutans,  which  did  poorly,  nor  A.  furcatus 
showed  signs  of  flower-stalks  by  the  last  of  August. 


Table  35. — Growth  of  species  in  cultivated  soil. 


Species. 

Degree  of  development  during  first  season. 

Agropyrum  glaucum . 

Good  growth  of  foliage;  maximum  2  feet;  no  flower-stalks. 

Andropogon  furcatus . 

Fine  bunches;  foliage  18  in.;  a  few  flower-stalks  36  to  38  in. 

halli . 

Foliage  16  in.;  flower-stalks  30  in.  (cf.  plate  12  c). 

nutans . 

Excellent  growth;  20  in.,  seeding  abundantly  at  3  to  4.5  feet. 

Aristida  purpurea . 

Large  bunches;  foliage  11  in.;  flower-stalks  18  in. 

Bouteloua  gracilis . 

Dense  growth;  leaves  14  in.;  flowering  profusely  at  15  to  22  in. 

hirsuta . 

Leaves  10  in.;  flower-stalks  appearing  Aug.  8;  later  12  in.  tall; 
abundant. 

racemosa . 

Good  growth;  ave.  height  13  in.;  flower-stalks  3  to  3.5  feet. 

Calamovilfa  longifolia.  .  . . 

Foliage  16  in.;  no  flower-stalks. 

Desmodium  canescens .... 

Flower-stalk  appearing  July  10;  fruited  abundantly  at  5  feet 
(cf.  plate  14  b). 

Elymus  canadensis . 

Foliage  2  feet;  flower-stalks  4  to  5  feet;  very  large  heads. 

Kuhnia  glutinosa . 

34  in.  tall;  fruiting  abundantly. 

Lespedeza  capitata . 

Fine  plants,  20  to  24  in.;  seeded  abundantly. 

Liatris  scariosa . 

3  to  6  in. ;  many  leaves  per  plant. 

Muhlenbergia  pungens .... 

9  in.;  flowered  and  seeded  profusely  at  14  to  16  in. 

Onagra  biennis . 

One  rosette  28  in.  in  diameter;  many  smaller  ones;  many  had 
flower-stalks  5  to  5.5  feet  tall;  blossomed. 

Panicum  virgatum . 

Average  height  foliage  29  in.;  seeded  abundantly  at  3  to  3.5  feet. 

Petalostemon  candidus.  .  . 

Excellent  growth;  very  much  bunched  stems,  8  to  12  in.  tall. 

Pinus  ponderosa . 

Five  plants,  4  to  5  in.  tall. 

Robinia  pseudacacia . 

Stems  nearly  an  inch  in  diameter  and  7.5  feet  tall. 

Sporobolus  asper . 

9  in.  tall;  flower-stalks  14  to  16  in.;  seeded  profusely. 

Stipa  viridula . 

Foliage  about  16  in.  tail;  maximum  26  in.;  no  flower-stalks. 

At  Nebraska  City,  6  of  the  13  species  of  seedlings  died  the  first  summer; 
Regardless  of  this  heavy  mortality,  all  the  species  survived  the  summer  of 
1922,  notwithstanding  the  drought.  However,  all  suffered  more  or  less 
severely  in  late  summer,  Stipa  comata  being  represented  by  remnants  only  at 
the  end  of  the  season.  Bouteloua  hirsuta  and  B.  gracilis  alone  blossomed. 
The  seedling  area,  although  quite  shaded  by  the  adjacent  vegetation,  was  not 
much  invaded. 

In  1923,  Stipa  comata  became  badly  invaded  and  died.  All  the  others  made 
a  good  growth. 

Effect  of  Competition. 

In  order  to  determine  the  effects  of  competition  upon  the  development  of 
the  species  investigated,  many  of  them  were  grown  in  a  cultivated  area  at 
Lincoln,  kept  free  from  weeds  by  hoeing,  and  watered  from  time  to  time 
(table  35). 


EDAPHIC  STATIONS!  SOD  TRANSPLANTS. 


105 


The  fine  growth  made  in  a  single  season  by  these  species  is  in  striking  con¬ 
trast  to  that  under  even  the  most  favorable  method  of  planting  in  the  grass¬ 
land  and  emphasizes  the  striking  effect  that  competition  plays  in  limiting 
plant  development  under  natural  conditions.  Plants  growing  for  a  second 
year  under  cultivation  made  no  less  remarkable  growth.  Bouteloua  gracilis 
had  an  average  height  of  foliage  of  19  inches,  spread  15  inches  on  either  side 
of  the  trench,  and  some  of  the  flower-stalks  were  32  inches  tall.  Agropyrum 
glaucum  was  29  inches  tall,  with  a  maximum  height  of  44  inches,  and  had 
spread  6  feet  by  rhizome  propagation.  A  single  plant  of  Onagra  biennis  had 
3  stems  which  reached  a  height  of  7  feet  and  12  others  of  lesser  height,  all 
from  the  same  rosette  (plate  14). 

Summary. 

A  summary  of  planting  experiments  is  given  in  table  36,  where  for  purposes 
of  comparison  the  high  prairie  is  included.  The  germination  of  surface- 
sown  seed  was  not  greatly  different  at  the  three  stations  (70  to  84  per  cent), 


Table  36. — Summary  of  planting  experiments ,  1922. 


Method  of 
seeding. 

Per  cent  of  germination. 

Per  cent  of  establishment  of 
germinated  species. 

High 

prairie. 

Low 

prairie. 

Nebraska 

City. 

High 

prairie. 

Low 

prairie. 

Nebraska 

City. 

Surface  sowing . 

82 

84 

70 

50 

25 

50 

Trench . 

70 

60 

62 

63 

64 

33 

Denuded  quadrat. . . . 

71 

81 

69 

72 

60 

54 

Average . 

74 

75 

67 

62 

50 

46 

Seedlings . 

70 

r  45 

59 

that  on  the  low  prairie  being  highest.  Germination  in  denuded  quadrats  was 
also  about  10  per  cent  greater  on  the  low  prairie  than  elsewhere,  Nebraska 
City  ranking  third.  Averaging  the  results  of  the  three  methods,  75  per  cent 
germination  occurred  on  low  prairie,  1  per  cent  less  on  high  prairie,  and  8  per 
cent  less  at  Nebraska  City. 

Because  of  the  effect  of  the  luxuriant  vegetation  of  the  low  prairie  in  reduc¬ 
ing  the  light  intensity,  a  factor  which  quite  outweighed  the  higher  water- 
content,  establishment  averaged  lower  here  (50  per  cent)  than  on  high  prairie 
(62  per  cent)  and  was  least  at  Nebraska  City  (46  per  cent).  The  last  fact  can  be 
directly  correlated  with  drought,  especially  when  it  is  recalled  that  the  surface 
sowing  at  Lincoln  was  watered.  Similar  conditions  hold  for  the  seedling  trans¬ 
plants.  A  survey  of  the  data  shows  clearly  that  while  surface  sowing  gave  the 
greatest  per  cent  of  germination,  the  best  establishment  occurred  in  the 
denuded  quadrats.  Compared  with  the  western  stations,  both  the  per  cent 
of  germination  and  establishment  averaged  higher. 

Sod  Transplants. 

Twenty-eight  blocks  of  soil,  comprising  25  species,  were  transplanted  from 
the  several  habitats  about  Lincoln  into  the  low  prairie  on  March  22.  These 
included  11  subdominant  forbs,  as  well  as  all  of  the  most  important  grasses. 


106 


EXPERIMENTS  DURING  1922. 


Agropyrum  glaucum  grew  poorly,  not  attaining  a  height  greater  than  11 
inches  and  failing  to  flower.  Astragalus  crassicarpus,  Brauneria  pallida, 
and  Psoralea  tenuiflora  floribunda,  all  provided  with  strong  tap-roots  neces¬ 
sarily  cut  off  in  transplanting,  languished  and  died  within  a  few  weeks.  All 
of  the  rest,  however,  came  through  the  season  in  good  condition,  75  per 
cent  of  the  dicotyls  and  50  per  cent  of  the  grasses  flowering. 

A  lot  of  sods,  including  11  species  from  Arizona,  were  transplanted  into 
low  prairie  early  in  May.  The  blocks  were  very  small,  being  only  3  or  4  inches 
in  diameter,  and  it  seems  probable  some  were  dead  when  transplanted.  In 
spite  of  sufficient  watering  the  following  did  not  grow:  Aristida  divaricata,  A. 
purpurea,  Bouteloua  eriopoda,  B.  hirsuta,  B.  racemosa,  Hilaria  mutica,  H.  cen¬ 
chroides,  Sporobolus  wrighti,  and  Valota  saccharata.  Andropogon  saccha- 
roides  put  forth  3  green  shoots,  which  reached  a  height  of  11  inches  before 
they  died  in  August.  Bouteloua  bromoides  and  Hilaria  cenchroides  formed 
good  clumps  5  to  8  inches  high,  the  former  bearing  flower-stalks  8  to  13 
inches  tall.  However,  both  were  winterkilled,  notwithstanding  the  fact  that 
they  were  well  covered  with  a  mulch  of  dead  grasses.  The  following  species 
from  Arizona  were  also  transplanted  into  high  prairie  at  the  same  time: 
Aristida  divaricata,  A.  purpurea,  Bouteloua  eriopoda ,  B.  bromoides,  B.  hirsuta 
(all  of  which  died  promptly),  and  Hilaria  cenchroides .  The  last  made  a 
sparse  growth,  reaching  a  height  of  8  to  10  inches  in  August,  but  died  under 
a  mulch  during  the  following  winter. 

Sod  of  14  species  of  grasses  from  both  high  and  low  prairie  were  trans¬ 
planted  into  the  salt-flat  near  the  low-prairie  station  late  in  March.  Andro¬ 
pogon  nutans,  A,  furcatus,  Panicum  virgalum,  and  Sporobolus  asper  did  very 
poorly,  making  only  a  sparse  growth,  yellowing  and  wilting  from  time  to  time. 
By  June  22  not  only  this  lot  of  transplants,  but  also  those  of  previous  years 
were  in  very  poor  condition.  Large  cracks  occurred  around  most  of  the  blocks 
of  sods  and  some  were  almost  dried  out.  Shading  played  rather  an  unim¬ 
portant  role,  since  the  height  of  the  Distichlis  was  only  18  inches.  Sporo¬ 
bolus  died  late  in  July,  and  the  others  made  a  fair  to  poor  growth  only. 
Nearly  all  were  more  or  less  dwarfed  and  of  a  light-green  color,  and  the 
inflorescences  were  often  reduced.  In  fact,  only  5  species  (36  per  cent) 
seeded;  these  were  Bidbilis  dadyloides,  Bouteloua  gracilis,  Elymus  canaden¬ 
sis,  Koeleria  cristata,  and  Stipa  spartea. 

On  April  5,  14  species  were  transplanted  into  the  former  swamp  area. 
Silting  up  since  the  building  of  a  dam,  as  well  as  the  enormous  losses  by 
transpiration  from  the  rank  growth  of  vegetation,  had  decreased  the  water- 
content.  On  June  7  the  holard  at  any  depth  did  not  exceed  22  per  cent,  which 
was  the  amount  in  the  surface  6  inches;  by  June  22  it  had  fallen  to  15  per 
cent  or  less  in  the  surface  2  feet.  It  seems  evident  that  there  was  no  excess 
moisture  or  deficient  aeration  and  that  light  was  the  controlling  factor.  By 
May  6,  Spartina  was  8  to  10  inches  tall,  and  it  had  reached  a  level  of  32  inches 
by  the  middle  of  June.  In  August  a  rank  growth  of  Spartina,  Phalaris,  etc., 
4  feet  tall,  covered  the  area;  light  readings  at  this  time  gave  values  of  1.5  to 
11  per  cent.  Andropogon  furcatus,  A.  scoparius,  and  Panicum  virgatum,  al¬ 
though  starting  out  well,  were  badly  invaded  by  the  swamp  dominants  and 
died  by  the  middle  of  July,  as  did  Andropogon  nutans  later  in  the  summer. 
All  suffered  severely  from  shading,  as  was  evidenced  by  the  attenuated  leaves 


EDAPHIC  STATIONS:  SOD  TRANSPLANTS. 


107 


and  slender  flower-stalks  of  the  5  species  that  blossomed,  viz,  Agropyrum, 
Bulbilis,  Elymus,  Koeleria,  and  Stipa.  The  species  of  the  following  genera 
came  through  the  season  in  fair  to  good  condition:  Agropyrum,  Bulbilis, 
Elymus,  Koeleria,  Spartina,  and  Stipa.  Bouteloua  gracilis,  B.  hirsuta,  B. 
racemosa,  and  Sporobolus  were  in  poor  condition  by  autumn. 

Duplicate  blocks  of  sods  of  the  following  species  were  shipped  from  Lincoln 
and  transplanted  at  Colorado  Springs  on  March  28:  Andropogon  scoparius, 
A.  furcatus,  A.  nutans,  Elymus  canadensis,  Sporobolus  asper,  Stipa  spartea, 
Koeleria  cristata,  Bouteloua  racemosa,  B.  gracilis,  B.  hirsuta,  Bulbilis  dacty- 
loides,  Panicum  virgatum,  Spartina  cynosuroides,  and  Agropyrum  glaucum. 
All  were  growing  vigorously  on  May  21,  but  were  considerably  eaten  by 
grasshoppers  and  doing  rather  poorly  by  July  4.  A  final  check  on  August  24 
showed  that  Bulbilis  dactyloides  alone  had  blossomed,  and  no  flower-stalks 
were  appearing  on  any  of  the  other  species.  Sporobolus  asper  had  died,  and 
Elymus,  Andropogon  furcatus,  and  B.  racemosa  were  eaten  back  to  mere  rem¬ 
nants.  Triplicate  sods  of  Stipa  viridula,  Muhlenbergia  gracilis,  M.  gracillima, 
and  Sporobolus  cryptandrus  were  shipped  from  Colorado  Springs  and  trans¬ 
planted  in  the  cultivated  plats  at  Lincoln  on  June  22.  The  sods  were  very 
small  and  the  plants  died  in  spite  of  ample  watering. 

Large  duplicate  blocks  of  sods  were  shipped  from  Lincoln  to  Berkelej^, 
California,  which  has  an  average  rainfall  of  24  inches,  occurring  chiefly  in 
the  winter  months,  and  a  long  dry  season  in  summer  and  autumn.  These 
were  transplanted  on  December  4  (1921),  the  species  employed  being  Andro¬ 
pogon  scoparius,  A.  furcatus,  A.  nutans,  Elymus  canadensis,  Stipa  spartea, 
Koeleria  cristata,  Bouteloua  racemosa,  and  Bulbilis  dactyloides.  The  sods  were 
set  on  a  dry  west  exposure  in  a  heavy  clay  soil  covered  chiefly  with  introduced 
weeds,  such  as  Arena  fatua,  Brassica  campestris,  and  Raphanus  saiivus. 
Owing  to  an  abundance  of  rain,  conditions  at  the  time  of  transplanting  were 
very  favorable  for  growth.  The  original  vegetation  was  bunch-grass  prairie 
composed  mostly  of  Stipa  setigera,  as  indicated  by  the  relicts  of  this.  Some 
attention  was  given  the  sods  in  1921  and  1922,  at  first  a  little  water,  and  then 
occasional  removal  of  the  competing  weeds.  Most  of  the  grasses  did  not 
survive  the  first  dry  season,  but  Elymus  canadensis  made  a  good  growth. 
Bulbilis  dactyloides  persisted  for  a  time,  and  Poa  pratensis  spread  at  first, 
but  succumbed  when  water  was  withheld.  Even  Elymus  was  unable  to  sur¬ 
vive  the  exceptionally  dry  spring  and  summer  of  1923,  and  the  plot  was 
finally  destroyed  by  the  great  fire  of  September  1923.  The  failure  of  the 
grasses  to  establish  themselves  was  due  chiefly  to  inability  to  pass  the  long 
dry  seasons  and  to  competition  as  a  contributing  factor,  but  the  experiment 
was  on  too  small  a  scale  to  justify  the  conclusion  that  none  of  the  species 
could  be  established. 

A  number  of  grasses  from  the  Santa  Rita  Reserve  near  Tucson,  Arizona, 
were  planted  under  the  same  conditions  at  Berkeley.  The  sods  were  set 
April  3,  1921,  and  comprised  Andropogon  saccharoides,  A.  coniortus,  Aristida 
divaricata,  A.  purpurea,  Bouteloua  bromoides,  B.  hirsuta,  B.  racemosa,  B.  roth- 
rocki,  B.  eriopoda,  Hilaria  cenchroides,  H.  mutica,  and  Sporobolus  wrighti. 
All  of  these  made  some  growth  in  1921,  but  by  the  autumn  of  1923  all  had 
succumbed  except  the  following:  Andropogon  saccharoides  grew  vigorously 
in  1922,  reaching  a  height  of  4  feet,  flowered,  and  set  seed  abundantly ;  in  1923 


108 


EXPERIMENTS  DURING  1922. 


the  3  plants  were  growing  and  flowering,  with  a  slight  tendency  to  increase 
but  not  spreading  over  the  ground,  and  no  seedlings  were  noticed;  Hilaria 
mutica  made  an  attempt  to  establish  itself  and  1  of  the  3  tufts  was  still  living; 
Aristida  divaricata  was  in  the  same  condition  as  the  Hilaria;  Bouteloua  bro- 
moides  made  a  good  start  and  flowered  in  1922,  but  disappeared  during  the 
long  dry  summer  of  1923 ;  Sporobolus  wrighti  grew  each  season,  and  although 
it  did  not  spread,  was  holding  its  own,  even  against  the  weedy  grasses  with 
which  it  had  to  compete  during  the  spring  and  early  summer.  It  is  instruc¬ 
tive  to  note  that  the  grasses  from  the  desert  plains  grew  better  than  those 
from  the  true  prairies,  a  fact  readily  explained  by  the  greater  similarity  in 
climate  and  climax  between  Arizona  and  California. 


5.  EXPERIMENTS  DURING  1923. 

DEVELOPMENT  OF  SEEDLINGS  AND  TRANSPLANTS. 

It  remains  only  to  trace  the  history  of  the  1922  plantings  through  the  period 
from  September  1922  to  the  end  of  the  summer  of  1923. 

I 

Physical  Factors. 

Water  Relations. 

The  fall  and  winter  of  1922  constituted  a  period  of  great  drought.  Some 
idea  of  its  intensity  may  be  gained  by  an  examination  of  the  rainfall  data  in 
table  37. 


Table  37. — Precipitation  from  August  1922  to  August  1923. 


Burlington. 

Phillipsburg. 

Lincoln. 

Total. 

Departure 
from  mean. 

Total. 

Departure 
from  mean. 

Total. 

Departure 
from  mean. 

August . 

3.04 

+  0.50 

1.13 

-1.77 

0.69 

-3.02 

September .... 

0.16 

-1.23 

0.94 

-1.58 

2.12 

-0.52 

October . 

0.18 

-0.75 

0.44 

-1.04 

1.42 

-0.40 

November. . . . 

1.44 

+  1.01 

0.40 

-0.28 

2.62 

+  1.77 

December .... 

0.00 

-0.63 

0.00 

-0.82 

0.06 

-0.61 

January . 

0.00 

-0.26 

0.00 

-0.44 

0.14 

-0.48 

February . 

0.10 

-0.36 

0.16 

-0.65 

0.66 

-0.04 

March . 

0.36 

-0.47 

1.31 

+0.52 

1.77 

+0.44 

April . 

1.66 

-0.40 

3.40 

+  1.07 

2.21 

-0.56 

May . 

No  report. 

.... 

7.86 

+4.85 

3.31 

-0.94 

June . 

3.03 

+0.26 

4.94 

+  1.03 

5.25 

+0.93 

Julv . 

4.33 

+  1.56 

2.34 

-0.62 

1.88 

-1.95 

August . 

4.89 

+2.30 

1.85 

-0.95 

.5.50 

+  1.79 

Although  Burlington  had  an  excess  of  0.5  inch  in  August,  drought  at  the 
other  stations  began  during  this  month.  Precipitation  was  below  normal 
at  Burlington  (except  during  November)  until  May,  and  the  same  was  true 
at  Lincoln  until  June,  except  a  slight  excess  in  March,  while  at  Phillipsburg 
it  was  exceedingly  low  until  March.  However,  it  should  be  noted  that  the 
spring  and  summer  rainfall  was  high  at  the  western  stations,  although  below 
normal  at  Lincoln  during  April  and  May  and  again  in  July.  The  season  was 
one  which  promoted  excellent  growth.  Not  only  was  the  rainfall  generally 
above  normal,  but  the  rains  were  also  well  distributed,  drought  periods  west¬ 
ward  being  fewer  and  shorter  than  usual.  This  was  indicated  by  the  excellent 
growth  of  Bouteloua  gracilis ,  which  reached  a  height  of  12  to  18  inches  at 
Burlington  and  also  by  the  fact  that  the  short-grasses  remained  green  or  dried 
only  slightly  throughout  the  entire  summer.  Conditions  were  slightly  less 
favorable  in  August  at  Lincoln  and  at  Phillipsburg,  where  the  three  grama 
grasses  ripened  seed.  On  the  whole,  vegetation  grew  well  at  Lincoln,  the 
grasses  on  the  gravel-knoll  remaining  green  all  summer.  An  examination  of 
the  chresard  taken  at  intervals  in  the  various  stations  (table  38)  is  illuminating 
in  this  connection. 

The  very  low  water-content  on  the  high  prairie  in  October  is  remarkable; 
on  the  gravel-knoll  practically  no  water  was  available  to  4  feet,  and  it  was  not 


109 


110 


EXPERIMENTS  DURING  1923. 


high  even  on  low  prairie.  By  March  1  a  good  water-content  was  found  at 
both  prairie  stations  and  available  moisture  to  the  amount  of  3  to  7  per  cent 
was  present  throughout  the  season.  The  adequate  holard  in  the  surface  layers 
at  Burlington  during  July  and  August  was  very  unusual.  At  Phillipsburg,  as 
already  indicated,  it  was  drier  in  August.  Because  of  the  drought  of  autumn 
and  late  winter,  many  species  under  all  methods  of  planting  and  transplanting 
were  killed  (table  39). 


Table  3S. — Holard  in  excess  of  hygroscopic  coefficient  at  the  several  stations,  1923  ( unless 

otherwise  indicated ) . 


Station. 

Date. 

Depth  in  feet. 

0  to  0.5 

0.5  to  1 

1  to  2 

2  to  3 

3  to  4 

i 

Lincoln: 

High  prairie . 

Oct.  27,1922 

1.8 

3.7 

3.0 

2.8 

3.8 

Do . 

Mar.  1 

18.1 

18.3 

12.1 

10.7 

7.3 

Do . 

June  2 

10.4 

16.6 

16.7 

11.5 

8.-2 

Do . 

July  23 

3.0 

4.3 

5.4 

7.1 

7.5 

Do . 

Aug.  3 

4.2 

5.4 

5.0 

6.4 

8.2 

Do . 

Aug.  23 

12.5 

16.4 

6.3 

7.1 

8.7 

Gravel-knoll . 

Oct.  27 

-1.5 

1.0 

-0.8 

1.5 

3.1 

Do . 

June  2 

-0.6 

1.0 

3.1 

9.8 

7.6 

Burlington . 

July  6 

0.4 

-0.7 

0.2 

0.8 

-0.6 

Do . 

July  19 

10.0 

0.0 

-0.3 

-0.2 

-0.2 

Do . 

Aug.  21 

5.8 

4.5 

-0.2 

-0.7 

-0.6 

Phillipsburg . 

June  20 

11.3 

13.3 

11.1 

12.6 

11.9 

Do . 

Aug.  22 

-0.6 

1.5 

0.7 

1.6 

5.6 

Nebraska . 

May  27 

20.9 

20.0 

17.7 

13.9 

12.7 

Do . 

Aug.  28 

22.7 

20.0 

9.5 

6.7 

7.7 

Lincoln: 

Low  prairie . 

Oct.  27 

3.5 

5.8 

6.2 

8.3 

13.2 

Do . 

Mar.  1 

22.4 

21.1 

11.8 

11.3 

16.4 

Do . 

Aug.  23 

11.4 

18.4 

13.4 

8.0 

14.0 

Survival  Results. 

An  examination  of  the  data  in  table  39  reveals  a  number  of  interesting  facts, 
the  two  most  important  of  which  are  as  follows:  Losses  at  the  three  major 
climatic  stations  were  greatest  at  Burlington,  intermediate  at  Phillipsburg, 
and  least  at  Lincoln.  The  losses  at  all  stations  averaged  highest  for  the 
plants  of  a  single  year’s  establishment,  next  for  those  2  years  old,  and  least 
for  those  established  for  3  seasons.  With  a  single  exception,  survival  was 
greatest  at  all  3  stations  under  the  method  of  denuded  quadrats,  this  even 
exceeding  that  of  transplanting  blocks  of  sods.  Surface  sowing  gave  the 
lowest  survival. 

Survival  on  the  low  prairie  and  at  Nebraska  City  was  very  similar,  following 
the  sequence  stated  above  as  regards  length  of  establishment.  Except  for 
1920  (when  all  averages  were  very  high)  it  exceeded  that  on  the  high  prairie  at 
Lincoln,  and  naturally  that  at  the  western  stations.  Survival  on  the  gravel- 
knoll  of  species  grown  for  at  least  two  summers  was  remarkably  high,  though 
few  species  were  concerned,  with  the  exception  of  sod  transplants. 


SURVIVAL  RESULTS. 


Ill 


Surface  Sowing. 

Nine  of  the  18  species  that  germinated  on  the  surface  of  the  high  prairie 
at  Lincoln  died  by  the  end  of  August.  Because  of  the  exceedingly  dry 
autumn  and  winter,  6  species  were  winterkilled,  leaving  only  33  per  cent  of 
the  survivors  of  the  first  summer.  Petalostemon  candidus  had  only  two  very 
delicate  plants  3  to  5  inches  tall  by  autumn,  but  A ndropogon  furcatus  and  A. 
nutans  had  both  made  a  good  growth,  reaching  a  height  of  10  or  12  inches. 


Table  39. — Comparative  survival  at  the  different  stations  during  fall  and  winter  of  1922-23. 


Method  of  planting. 

Lincoln, 

high 

prairie. 

Phillips¬ 

burg. 

Burling¬ 

ton. 

Method  of  planting. 

Lincoln, 

low 

prairie. 

Nebraska 

City. 

Gravel- 

knoll. 

1920. 

1920. 

Surface  sowing .... 

,  ,  , 

.  .  . 

100 

Surface  sowing .... 

... 

... 

... 

Trench  planting .  .  . 

100 

100 

•  .  • 

Trench  planting  .  .  . 

100 

100 

... 

Denuded  quadrats . 

100 

100 

100 

Denuded  quadrats. 

100 

88 

... 

Seedlings . 

60 

Seedlings . 

Sod  transplants. . .  . 

94 

... 

52 

Sod  transplants. . .  . 

79 

94 

Average . 

98 

100 

84 

Average . 

93 

94 

94 

1921. 

1921. 

Surface  sowing.  .  .  . 

... 

50 

... 

Surface  sowing .... 

... 

100 

... 

Trench  planting .  .  . 

100 

50 

.  .  . 

Trench  planting .  .  . 

.  .  . 

100 

... 

Denuded  quadrats. 

100 

100 

50 

Denuded  quadrats. 

80 

100 

67 

Seedlings . 

60 

68 

Seedlings . 

100 

88 

100 

Sod  transplants .... 

94 

63 

Sod  transplants .... 

100 

100 

Average . 

89 

72 

57 

Average . 

93 

97 

89 

1922. 

1922. 

Surface  sowing .... 

33 

38 

... 

Surface  sowing .... 

17 

57 

Trench  planting .  .  . 

40 

50 

0 

Trench  planting .  .  . 

78 

50 

Denuded  quadrats. 

78 

72 

22 

Denuded  quadrats . 

85 

75 

Seedlings . 

79 

50 

20 

Seedlings . 

70 

85 

Sod  transplants. . . . 

86 

17 

Sod  transplants .... 

80 

Average . 

63 

53 

15 

Average . 

,  66 

67 

. . . 

In  the  mixed  prairie  at  Phillipsburg,  8  species,  4  of  which  were  in  very  poor 
condition,  survived  the  first  season.  Andropogon  nutans,  A.  furcatus,  Des- 
modium  canescens,  Elymus  canadensis,  and  Kuhnia  glutinosa  were  winter- 
killed,  leaving  only  the  3  species  of  Bouteloua.  None  of  these  had  seeded 
by  the  following  August,  but  all  were  in  fair  condition,  having  reached 
heights  of  4  to  8  inches.  None  of  the  surface-sown  plants  survived  the 
summer  at  Burlington. 

Trench  Sowing. 

Of  the  species  sown  in  a  trench  on  the  high  prairie,  63  per  cent  lived  through 
the  first  season,  most  of  them  being  badly  dried  out  late  in  August;  5  of  the  10 
did  not  grow  the  next  spring,  viz,  Andropogon  furcatus,  Aristida  purpurea, 
Elymus  canadensis,  Liatris  scariosa,  and  Rohinia  pseudacacia.  Andropogon 
nutans  and  Pinus  ponderosa  had  succumbed  by  August  of  1923,  leaving  only 
several  fine  clumps  of  Bouteloua  racemosa  and  4  good  plants  of  Desmodium 
canescens,  each  about  8  inches  tall.  Plants  in  the  trench  at  Phillipsburg  were 
represented  in  the  fall  of  1922  by  Andropogon  nutans  and  Bouteloua  racemosa 
only.  The  last  was  winterkilled,  while  Andropogon  was  represented  by  very 
much  attenuated  plants  8  inches  tall,  the  shade  being  very  dense  again  during 
1923.  At  Burlington,  Andropogon  nutans  alone  survived  the  summer,  but  it 
died  the  following  fall  or  winter. 


112 


EXPERIMENTS  DURING  1923. 


Denuded  Quadrats. 

Of  the  25  species  that  grew  in  the  denuded  quadrats  on  the  high  prairie, 
18  survived  the  first  summer.  Of  these,  Aristida  purpurea,  Desmodium 
canescens,  Onagra  biennis,  and  Pinus  ponder osa  succumbed  by  spring.  Andro- 
pogon  scoparius  and  Muhlenbergia  pungens,  which  were  represented  by  a  single 
clump  each,  died  before  September  1923.  Acer  saccharinum  was  killed  back 
to  within  6  inches  of  the  soil,  16  of  the  trees  dying;  however,  like  all  the  other 
species,  they  made  a  good  growth  during  the  summer.  Exceptions  to  this 
were  Bouteloua  gracilis,  Sporobolus  asper,  and  Robinia  pseudacacia,  which  did 
poorly.  None  of  the  species  blossomed.  The  quadrats  were  only  slightly 
invaded.  It  is  interesting  that  not  only  grasses  and  forbs,  but  also  certain 
trees,  survived  the  second  summer. 

At  Phillipsburg  only  half  of  the  species  that  germinated  in  the  denuded 
quadrats  lived  to  the  end  of  the  first  summer.  Andropogon  furcatus, 
Gleditsia  triacanthus,  and  Acer  saccharinum  were  winterkilled.  Although  all 
quadrats  were  densely  shaded  by  a  rank  growth  of  Bouteloua  gracilis  18  to  24 
inches  high,  the  8  remaining  species  all  did  well.  Aristida  purpurea  failed  to 
blossom,  as  did  also  Andropogon  nutans  and  Panicum  virgatum.  The  rest, 
viz,  Bouteloua  racemosa,  B.  gracilis,  Sporobolus  asper,  and  Petalostemon  can- 
didus,  seeded,  the  last  at  a  height  of  2  to  2.5  feet.  At  Burlington,  64  per  cent 
survived  in  the  denuded  quadrats.  Because  of  the  very  dry  fall  and  winter 
that  ensued,  only  2  of  the  9  species  showed  renewed  growth  the  following 
spring.  Bouteloua  gracilis  formed  excellent  clumps  and  flowered  profusely 
in  1923.  Elymus  canadensis,  the  other  survivor,  was  represented  by  a 
single  stalk  which  headed  at  16  inches. 

Seedling  Transplants. 

Of  the  seedlings  transplanted  into  high  prairie  in  the  spring  of  1922, 
only  70  per  cent  survived,  notwithstanding  that  they  had  been  regularly 
watered  throughout  the  summer.  Of  the  14  survivors,  Elymus,  Petalostemon, 
and  Argemone  were  winterkilled.  Onagra  died  during  the  following  summer, 
but  all  of  the  others  made  a  good  growth,  though  none  came  into  blossom. 
Of  the  19  species  of  seedlings  grown  in  the  mixed  prairie,  15  survived, 
but  8  of  these  were  winterkilled.  Although  the  rest  made  a  good  growth 
during  the  following  summer,  Bouteloua  gracilis  and  Ratibida  columnaris 
alone  came  into  bloom.  At  Burlington  only  5  of  the  19  species  trans¬ 
planted  survived.  All  but  one  were  winterkilled,  viz,  Sporobolus,  Bouteloua 
racemosa,  B.  hirsuta ,  and  Stipa  viridula,  Bouteloua  gracilis  alone  surviving. 
This  did  fairly  well  in  1923,  but  produced  no  flower-stalks. 

EXPERIMENTS  AT  EDAPHIC  STATIONS. 

Survival  Results. 

Surface  Sowing. 

On  the  low  prairie,  owing  to  dense  shading,  only  25  per  cent  of  the  1922 
surface-sown  plants  survived  the  first  summer.  Aristida,  Andropogon 
furcatus,  A.  nutans,  Bouteloua  gracilis,  B.  racemosa,  and  Petalostemon  candidus 
did  not  grow  the  following  spring.  Andropogon  nutans  alone  survived,  and  at 
the  end  of  the  following  summer  the  slender  plants  were  a  foot  high. 


EDAPHIC  STATIONS!  SURVIVAL. 


113 


At  Nebraska  City,  50  per  cent  of  the  species  survived.  Bouteloua  hirsuta, 
Elymns  canadensis,  and  Kuhnia  glutinosa  were  winterkilled  and  Bouteloua 
racemosa  died  by  the  end  of  the  next  summer.  Andropogon  nutans,  A.  fur- 
catus,  and  Liatris  punctata  alone  survived.  In  all  cases  the  plants  were  very 
much  attenuated  and  it  seemed  doubtful  if  they  would  ecize. 

Trench  Sowing. 

As  regards  the  trench  plantings  in  the  low  prairie,  9  species,  i.  e.,  64  per 
cent  of  those  that  germinated,  grew  throughout  the  first  summer.  Aristida 
and  Kuhnia  were  winterkilled  and  Andropogon  furcatus  died  the  following 
summer.  All  the  remaining  species  were  very  slender,  Elymus  and  Petalo- 
stemon  being  represented  in  August  by  remnants  only.  Andropogon  nutans, 
Bouteloua  gracilis,  B.  racemosa,  and  Desmodium  canescens,  which  made  up 
the  remainder,  reached  heights  of  6  to  8  inches,  but  none  seeded.  Of  the  21 
species  planted  in  the  Nebraska  City  trench,  only  4  survived,  and  of  these 
Kuhnia  glutinosa  and  Robinia  pseudacacia  were  winterkilled.  Andropogon 
nutans  and  Bouteloua  racemosa  were  each  represented  by  clumps  of  rather 
slender  plants  at  the  end  of  the  following  summer. 

Denuded  Quadrats. 

On  the  low  prairie  at  Lincoln,  60  per  cent  of  the  1922  plantings  in  quadrats 
survived,  Amorpha  canescens  and  Onagra  biennis  alone  succumbing  dur¬ 
ing  the  following  winter.  At  the  end  of  August  1923,  the  following  were  in 
very  poor  condition,  being  represented  by  remnants  only:  Bouteloua  gracilis, 
B.  hirsuta,  Sporobolus  asper,  and  Acer  saccharinum.  The  7  remaining  species, 
although  somewhat  slender,  had  made  fair  to  good  growth,  but  none  seeded. 
At  Nebraska  City,  12  species  survived  the  first  summer.  A  fourth  of  these, 
including  Andropogon  furcatus,  Desmodium,  and  Kuhnia  were  winterkilled, 
and  Robinia  pseudacacia  died  later.  All  of  the  remaining  species  made  good 
growth,  Andropogon  nutans  forming  a  dense  sod. 

Seedling  Transplants. 

Of  the  species  transplanted  as  seedlings  into  the  low  prairie,  45  per  cent 
survived  the  first  summer,  but  among  these  Stipa  viridula,  Petalostemon 
candidus,  and  Kuhnia  were  winterkilled.  All  the  rest,  including  the  3 
gramas,  Sporobolus,  Desmodium,  and  Andropogon  nutans,  prospered  until  the 
end  of  the  growing-season. 

At  the  Nebraska  City  station,  13  species  (59  per  cent)  lived  to  the  end  of 
the  first  summer.  Petalostemon  and  Ratibida  were  winterkilled.  All 
of  the  others  made  a  good  growth  because  of  the  favorable  season,  with  the 
exception  of  Onagra,  which  died  in  midsummer. 

Summary  of  Survival. 

The  fate  of  the  1922  plantings  by  the  end  of  1923  is  shown  in  table  40. 

Under  all  methods  of  planting  or  transplanting,  the  survival  at  the  end  of 
the  second  season  of  growth  was  greatest  at  Lincoln,  intermediate  at  Phillips- 
burg,  and  least  at  Burlington.  Of  the  several  methods  of  planting,  survival 
in  the  trench  was  lowest  and  surface  sowing  next,  while  the  denuded  quadrats 
were  only  slightly  more  successful  than  the  seedling  transplants.  The  average 
survival  on  the  low  prairie  at  Lincoln  was  greater  than  at  Nebraska  City, 
but  the  latter  was  nearly  equal  to  that  on  high  prairie  at  Lincoln.  On  low 
prairie  and  at  Nebraska  City  the  success  of  the  several  methods  of  seeding 
was  in  the  same  order  as  at  the  other  stations,  except  that  trench  planting 


114 


EXPERIMENTS  DURING  1923. 


outranked  surface  sowing.  The  average  survival  of  the  seedling  transplants 
at  these  stations  was  less  than  on  high  prairie  (where  they  were  watered  the 
first  season),  but  exceeded  that  in  mixed  prairie. 

An  examination  of  the  species  which  gave  the  greatest  percentage  of  sur¬ 
vival  is  of  interest.  As  to  surface  sowing,  Petalostemon,  Andropogon  nutans , 
and  A.  furcatus  alone  survived  at  Lincoln,  and  the  three  boutelouas  at  Phillips- 
burg,  so  far  as  the  three  major  stations  are  concerned.  However,  Andropogon 
nutans  survived  in  the  two  stations  at  Lincoln  as  well  as  at  Nebraska  City, 
and  A.  furcatus  on  high  prairie  and  at  Nebraska  City.  Liatris  punctata  was 
the  only  other  survivor  and  was  found  at  Nebraska  City  alone. 


Table  40. — Summary  of  survival  of  1922  plantings  in  August  1923. 


Method  of  seeding. 

Lincoln. 

Phillips¬ 

burg. 

Burling¬ 

ton. 

Lincoln 

(low 

prairie). 

Nebraska 

City. 

Surface  sowing . 

17 

16 

0 

6 

21 

Trench . 

13 

13 

0 

43 

15 

Denuded  quadrats . 

48 

36 

14 

50 

36 

Average . 

26 

22 

5 

33 

24 

Seedlings . 

60 

37 

5 

39 

45 

In  the  trench,  Bouteloua  racemosa  and  Desmodium  were  the  sole  survivors  at 
Lincoln,  and  Andropogon  nutans  at  Phillipsburg,  while,  as  before,  none  were 
found  at  Burlington.  But  Bouteloua  racemosa  also  survived  at  Nebraska  City 
and  on  the  low  prairie  and  Andropogon  nutans  at  both  of  these  stations  also. 
Desmodium  persisted  on  low  prairie  as  well  as  on  high  prairie.  The  only 
other  survivors  occurred  on  the  low  prairie  alone,  viz,  Elymus,  Petalostemon , 
and  Bouteloua  gracilis . 

With  respect  to  denuded  quadrats,  Bouteloua  gracilis  persisted  at  all  five 
stations,  B.  racemosa  and  Andropogon  nutans  at  all  but  Burlington,  Petalo¬ 
stemon,  Panicum ,  and  Sporobolus  at  three,  and  Andropogon  furcatus,  Kuhnia, 
Liatris  scariosa,  Gleditsia,  Acer  saccharinum,  and  Elymus  at  two,  while  the 
following  were  found  at  only  one  station  each:  Robinia,  Bouteloua  hirsuta, 
Desmodium  (at  Lincoln),  Pinus,  and  Acer  negundo  (at  Nebraska  City). 

Among  the  seedlings,  Bouteloua  gracilis  occurred  at  all  the  stations,  and 
B.  hirsuta  and  Sporobolus  at  all  but  Burlington.  Liatris  scariosa,  Andropogon 
nutans,  Bouteloua  racemosa,  Stipa  spartea,  and  Desmodium  were  found  at 
three  stations,  while  Ratibida  columnaris  occurred  at  two.  The  following 
were  represented  at  one  station  only:  Liatris  punctata,  Koeleria  (at  Lincoln), 
Petalostemon  (at  Phillipsburg),  Kuhnia ,  and  Elymus  (at  Nebraska  City). 

Arranging  the  species  in  order  of  their  survival  under  all  methods  of  planting 
at  the  several  stations  gives  Andropogon  nutans  14,  Bouteloua  gracilis  12, 
B.  racemosa  11,  Sporobolus  and  Desmodium  each  7,  Petalostemon  and  Bouteloua 
hirsuta  each  6,  Andropogon  furcatus  and  Liatris  scariosa  each  5,  Elymus 
canadensis  4,  Panicum  virgatum,  Kuhnia  glutinosa,  and  Stipa  spartea  each  3, 
Liatris  punctata,  Gleditsia  triacanthus,  Acer  saccharinum,  and  Ratibida  colum¬ 
naris  each  2,  while  the  following  occurred  only  once:  Robinia  pseudacacia, 
Pinus  ponderosa,  Acer  negundo,  and  Koeleria  cristata. 


EDAPHIC  STATIONS!  SURVIVAL. 


115 


Bouteloua  gracilis  was  the  only  species  which  survived  under  some  method 
of  planting  at  all  5  stations.  The  following  persisted  at  both  Lincoln  and 
Phillipsburg,  but  not  at  Burlington:  Petaloslemon,  Andropogon  nutans, 
Bouteloua  racemosa,  B.  hirsuta,  Panicum,  Sporobolus,  Stipa  spartea,  Ralibida, 
and  Liatris  scariosa. 

Sod  Transplants. 

As  to  the  1922  sod  transplants  on  the  high  prairie,  the  following  died  during 
the  fall  or  winter:  Anemone ,  Grindelia,  Helianthus,  and  one  lot  of  Bouteloua 
gracilis,  while  Astragalus  crassicarpus  died  before  autumn.  Aside  from  the 
grasses,  nearly  all  of  which  made  an  excellent  growth,  it  is  interesting  to 
note  that  several  forbs,  viz,  Liatris  scariosa,  Solidago  missouriensis,  and  S. 
rigida,  blossomed  profusely. 

At  Burlington  the  fall  and  winter  were  so  extremely  dry  that  83  per  cent 
were  winterkilled,  including  9  species.  This  left  a  single  sod  of  each  of  the 
following:  Agropyrum,  Bouteloua  gracilis,  Panicum  virgatum,  and  Andropogon 
scoparius.  The  last  died  before  the  end  of  the  summer.  Agropyrum  was 
represented  by  only  3  shoots  and  Panicum  by  2,  neither  species  blossoming, 
but  Bouteloua  gracilis  made  a  good  growth  and  put  forth  flower-stalks  abun¬ 
dantly.  The  contrast  between  prairie  and  plains  is  consequently  very  sharp 
and  the  disaster  met  by  planted  or  transplanted  species  in  the  latter  area 
needs  no  emphasis.  The  indications  in  1923  were  that  Bouteloua  gracilis  and 
possibly  Agropyrum  glaucum  were  the  only  species  that  would  survive  per¬ 
manently. 

Sods  transplanted  to  the  low  prairie  in  1922  were  winterkilled  to  the  extent 
of  5  species,  while  Agropyrum,  Bouteloua  gracilis,  and  Bouteloua  hirsuta  died 
the  following  summer.  By  the  end  of  the  season  Koeleria  and  Anemone 
were  nearly  dead,  due  to  the  severe  competition  and  dense  shade.  Although 
all  of  the  other  species  were  still  prospering,  the  condition  of  the  transplants 
made  in  1920  and  1921  indicated  that  a  year  or  two  would  suffice  to  eliminate 
the  upland  species  and  leave  the  taller  subclimax  grasses  and  forbs  in  pos¬ 
session  of  the  area. 

None  of  the  1922  sods  in  the  salt-flat  were  winterkilled,  but  Bouteloua 
hirsuta  died  the  following  summer.  In  August  1923,  Koeleria  was  represented 
by  mere  remnants,  while  several  of  the  other  species  evidenced  by  their  paler 
color  and  dwarfed  habit  the  uncongenial  nature  of  the  habitat,  notwith¬ 
standing  the  rather  wet  season.  However,  all  did  fairly  well,  but  several 
failed  to  bloom. 

As  to  the  species  transplanted  into  the  former  swamp  area  in  1922,  Sporo¬ 
bolus  and  two  lots  each  of  Bouteloua  hirsuta  and  B.  racemosa  failed  to  grow  the 
following  spring.  The  slough-grass  cast  a  very  dense  shade,  and  by  the  end  of 
1923  Bulbilis,  Elymus,  and  Bouteloua  gracilis  had  died,  while  Agropyrum  was 
represented  by  mere  remnants.  This  left  Spartina,  which  had  made  a  normal 
growth,  Stipa  spartea,  the  flowers  of  which  were  still  in  the  leaf-sheath  in  late 
August,  and  Koeleria,  which  failed  to  blossom.  In  another  season  it  is 
probable  that  these  two  high-prairie  species  would  also  have  been  eliminated. 

The  sods  planted  in  1922  at  Colorado  Springs  did  poorly  because  of  grazing. 
By  the  end  of  the  second  summer,  Andropogon  furcatus,  Panicum  virgatum, 
and  Bouteloua  racemosa  had  died,  and  Elymus  and  Spartina  were  represented 
by  mere  remnants.  None  but  Bulbilis  had  blossomed. 


116 


EXPERIMENTS  DURIN&  1923. 


PHYTOMETRIC  RESULTS. 

Transpiration  and  Growth. 

Plan. 

In  order  to  obtain  further  light  as  to  the  climatic  differences  of  the  major 
stations  in  terms  of  functional  response,  a  special  investigation  was  made  of 
transpiration  and  growth  during  the  summer  of  1923.  Plants  of  Helianthus 
annuus,  Avena  sativa,  Elymus  canadensis ,  and  Acer  negundo  were  grown  from 
seed  or  transplanted  as  seedlings  into  sheet-metal  containers  of  appropriate 
shape  and  sufficient  size  to  accommodate  the  root  systems  throughout  the 
duration  of  the  experiment.  After  the  plants  were  well  established,  the  leaf 
area  and  the  weight  of  plant  and  container  were  determined.  They  were 
then  installed  at  the  several  stations,  together  with  a  complete  battery  of 
instruments,  for  a  period  of  14  days,  and  measurements  made  of  transpiration 
and  growth  in  terms  of  increased  area.  The  considerable  differences  in 
altitude  and  hence  in  seasonal  development  made  simultaneous  studies  unde¬ 
sirable,  and  consequently  the  periods  of  observation  were  successive.  This 
was  also  imperative  because  of  the  time  and  effort  involved. 

b 

Methods. 

The  individual  plants  of  sunflower  and  box-elder  were  placed  in  cylindrical 
galvanized-iron  containers  5  to  6  inches  in  diameter  and  9  to  10  inches  deep, 
filled  with  rich  loam  soil  tamped  firmly  in  place.  A  layer  of  one-half  inch  of 
coarse  gravel  in  the  bottom  of  the  container  covered  an  exit-tube,  consisting 
of  an  automobile  tire  valve-stem  with  the  inner  end  cut  off  and  covered  with  a 
fine  copper  gauze  soldered  in  place.  The  core  of  each  tube  had  been  removed. 
The  tube  was  soldered  in  place  with  the  threads  projecting  through  the  wall 
of  the  container,  so  that  an  exhaust  pump  could  be  attached  for  aerating  the 
soil.  The  tube  also  assisted  materially  in  watering  the  plants,  the  usual  cap 
preventing  loss  during  the  intervals.  The  soil  was  well  screened,  brought  to  an 
optimum  holard,  and  weighed  at  the  time  of  filling  the  containers.  By 
restoring  the  containers  to  their  original  weight  from  time  to  time,  the  holard 
was  maintained  at  the  desired  level.  To  prevent  loss  other  than  by  transpira¬ 
tion,  the  containers  were  furnished  with  a  sloping  metal  top  provided  with  a 
circular  opening  with  the  edges  reamed  upward,  and  large  enough  to  receive  a 
cork  2.5  inches  in  diameter.  An  effective  seal  was  formed  by  boring  a  hole 
large  enough  for  the  plant  stem,  splitting  the  cork  and  fitting  it  into  place 
after  padding  the  sides  of  the  opening  with  a  little  cotton.  The  seal  was  tested 
by  a  check  container  without  a  plant,  but  fitted  with  a  wooden  peg  to  simulate 
the  plant  stem.  During  the  period  of  14  days  this  did  not  lose  water  in  an 
amount  sufficient  to  be  detected  by  a  balance  sensitive  to  2  grams  under  a 
load  of  7  kg. 

The  containers  for  wild  rye  and  oats  were  similar  to  those  already  described, 
except  for  the  tops,  which  were  furnished  with  a  slit  5  inches  long  and  1  inch 
wide.  The  edges  of  the  metal  cut  in  making  the  slit  were  turned  down  into 
the  container  about  a  quarter  of  an  inch  on  each  side  and  a  half-inch  at  the 
ends  of  the  slit.  These  furnished  supports  for  narrow  strips  of  shellacked  oak, 
which  were  held  in  place  by  thin  wedges  of  similar  material  at  each  end. 
These  were  put  in  place  after  the  containers  had  been  filled  and  the  soil  pressed 


TRANSPIRATION  AND  GROWTH. 


117 


firmly  under  the  metal  tops.  They  were  then  coated  with  shellac,  so  that  no 
openings  remained  except  between  the  wooden  strips,  which  narrowed  the 
slit  to  about  10  mm.  The  seeds  were  planted  through  this  opening,  which  was 
nearly  filled  with  soil  kept  moist  by  frequent  watering.  After  the  plants  came 
up,  the  remainder  of  the  opening  was  filled  with  sand  level  with  the  top  of  the 
wooden  strips.  The  containers  were  provided  with  felt  tops,  cut  to  fit  around 
the  slits,  and  sunken  level  with  the  soil.  The  efficiency  of  the  sand-mulch  in 
preventing  water-loss  was  found  to  be  high,  only  6  grams  escaping  in  a  period 
of  2  weeks.  Twelve  plants  of  average  size  were  selected  from  the  several 
containers  and  the  leaf-area  determined.  From  this,  and  the  number  of  plants 
in  each  container,  the  initial  area  of  the  group  of  plants  in  any  container  was 
calculated.  The  final  area  was  determined  in  a  similar  manner.  This  method 
was  used  because  it  was  quite  impossible  to  determine  the  total  area  of  the 
plants  in  place,  as  could  be  done  with  the  dicotyls. 

Owing  to  cool,  wet  weather,  the  plants  grew  slowly,  except  during  the  last 
week  of  May.  They  were  kept  covered  during  rains  and  at  night,  watered 
from  a  burette,  and  aerated  from  time  to  time.  To  keep  the  metal  containers 
from  heating  the  soil,  they  were  surrounded  by  sand  and  the  top  covered  by 
a  collar  of  felt  about  a  centimeter  thick,  held  in  place  by  strips  of  adhesive 
tape.  On  June  1  the  leaf-area  was  determined  by  means  of  solio  prints  and 
the  planimeter,  corks  were  inserted,  and  the  containers  (with  collars  removed) 
brought  back  to  their  initial  weight  after  they  had  been  transported  to  the 
station  in  the  high  prairie  at  Lincoln.  Here  they  were  placed  in  the  soil  and 
thoroughly  covered  after  the  collars  had  been  replaced,  the  exposed  plants 
being  sheltered  during  rains. 

After  the  14-day  period  of  the  experiment,  following  final  weighings, the 
number  of  parent  plants  and  number  of  tillers  in  each  container  was  ascer¬ 
tained.  Eighteen  specimens  of  each  group  were  then  selected  and  their  areas 
determined.  From  these  data  the  final  areas  were  calculated. 

Conditions  and  Results  at  Lincoln. 

Physical  Factors. 

The  period  (May  31  to  June  15)  was  exceptionally  cool  and  wet.  Only  one 
entire  day  was  sunny,  and  the  sun  shone  for  over  half  of  the  time  on  two  others 
alone.  During  a  4-day  interval  the  sun  did  not  appear,  while  the  total  sun¬ 
shine  over  the  whole  period  was  approximately  5.5  days.  A  total  of  4.9 
inches  of  rain  fell  during  8  days,  and  rains  occurred  in  the  daytime  on  6  days, 
during  one  of  which  it  was  necessary  to  keep  the  plants  sheltered  for  the 
entire  day.  In  fact,  they  were  under  cover  for  a  total  period  of  30  hours  of 
daylight  in  which  rain  was  falling. 

The  air-temperature  during  the  first  7  days  ranged  from  55°  to  91°  F.,  while 
the  humidity  was  never  lower  than  55  per  cent.  This  was  followed  by  a  period 
of  4  days  when  the  temperature  remained  at  58°  to  65°  F.  and  the  humidity 
above  80  per  cent.  The  remaining  time  was  similar  to  that  of  the  first  7  days. 
The  average  day  temperature  for  the  entire  period  was  70.1°  F.  and  the  day 
humidity  75  per  cent.  The  soil  temperature  at  a  depth  of  6  inches  among  the 
containers  varied  from  62°  to  71°  F.  The  total  wind  movement  at  a  height  of 
39  cm.  during  the  period  was  1,282  miles,  an  average  of  only  3.6  miles  per 
hour.  The  exceptionally  mesophytic  conditions  are  shown  by  the  average 


118 


PHYTOMETRIC  RESULTS 


Table  41. — Water-loss  and  growth  at  Lincoln. 
Helianthus  annuus. 


Water  added 

/*N 

TJ 

-tT  c3 

(grams) . 

Final  weight, 

June  15  (gran 

CO 

3 

OS 

a 

-d 

•  M 

o 

GO 

Con¬ 

tainer. 

Initial  weigl 
June  1  (gi 

June 

4. 

June 

12. 

June 

14. 

Total  water 

(grams) . 

Initial  area 

(sq.cm.). 

Final  area. 

(sq.  cm.) 

Average  are 

1  (sq.cm.). 

Loss  per  sq. 

(grams) . 

P.  ct.  increa 

area. 

1 

6,748 

300 

250 

100 

6,464 

934 

229.1 

960.5 

594.8 

15.7 

319.2 

2 

7,053 

300 

250 

100 

6,700 

1,003 

266.9 

1,135.5 

701.2 

14.3 

325.4 

3 

7,035 

300 

250 

100 

6,690 

995 

237.9 

1,142.4 

690.1 

14.4 

380.2 

4 

6,793 

300 

250 

100 

6,587 

856 

167.0 

1,029.1 

598.1 

14.3 

516.2 

5 

6,942 

300 

250 

100 

6,769 

823 

156.7 

1,075.9 

616.3 

133 

586.6 

6 

6,966 

300 

250 

100 

6,660 

956 

258.5 

1,099.4 

678.9 

141 

325.3 

7 

6,898 

300 

250 

100 

6,646 

902 

201.0 

1,127.9 

664.5 

135 

461.1 

8 

6,700 

300 

250 

100 

6,452 

898 

202.7 

921.1 

561.9 

159 

354.4 

9 

6,974 

300 

250 

100 

6,629 

995 

177.3 

1,124.4 

650.8 

153 

534.2 

10 

6,800 

300 

250 

100 

6,516 

934 

244.2 

928.8 

586.5 

159 

280.3 

11 

6,980 

300 

250 

100 

6,655 

975 

275. 1 

1,205.7 

740.4 

132 

338.2 

12 

6,962 

300 

250 

100 

6,672 

940 

187.5 

1,106.1 

646 . 8 

145 

489.9 

Aver .... 

145 

409.2 

A  VENA  SATIVA. 

Initial  weight, 

June  1  (grams). 

Water  added 
(grams) . 

Final  weight, 

June  1  (grams). 

'g 

<8 

3 

<73 

a 

T3 

a 

•  ri 

V 

CO 

Con¬ 

tainer. 

June 

7. 

June 

13. 

June 

15. 

Total  water 
(grams). 

Initial  area 
(sq.  cm.). 

Final  area 
(sq.  cm.). 

Average  are 
(sq.  cm.). 

Loss  per  sq. 
(grams) . 

P.  ct.  increa 

area. 

1 

8,918 

600 

300 

8,442 

1,376 

414.0 

1,601.7 

1 

,007.8 

136 

286.9 

2 

8,360 

500 

180 

8,081 

959 

414.0 

1,620.8 

1 

,017.4 

94 

291.5 

3 

8,233 

500 

120 

7,885 

968 

414.0 

1,614.4 

1,014.4 

95 

290.0 

4 

8,221 

500 

0 

7,860 

861 

414.0 

1,544.0 

979.0 

88 

272.9 

5 

8,237 

500 

0 

7,927 

810 

414.0 

1,436.1 

925.0 

87 

246.8 

6 

8,316 

500 

138 

8,004 

950 

414.0 

1,596.7 

1 

,005.4 

94 

99 

285.6 

278.9 

ElYMUS  CANADENSIS. 

1-31 

5,273 

100 

0 

5,186 

187 

145.4 

492.6 

319.0 

59 

238.8 

2-40 

5,010 

100 

100 

4,896 

314 

187.6 

635.7 

411.6 

76 

238.8 

3-41 

5,010 

100 

100 

4,916 

294 

192.3 

651.6 

421.9 

69 

238.8 

4-28 

5,206 

100 

0 

5,070 

236 

131.3 

445.0 

288.1 

82 

238.8 

5-43 

5,180 

100 

100 

5,044 

336 

201.7 

683.3 

442.5 

76 

238.8 

Control . 

5,093 

0 

0 

5,087 

6 

238.8 

Aver .... 

72 

238.8 

Acer  negundo. 

1 

4,355 

4,306 

49 

38.6 

67.6 

53.1 

92 

75.1 

2 

6,104 

.  .  • 

6,049 

55 

42.2 

107.6 

74.9 

72 

155.5 

3 

5,910 

,  ,  , 

5,872 

38 

36.2 

45.6 

40.9 

93 

25.9 

4 

6,363 

80 

6,300 

143 

99.2 

241.2 

170.2 

84 

143.1 

5 

5,933 

5,878 

55 

58.8 

72.6 

65.7 

84 

23.4 

Aver.  .  .  . 

85 

84.6 

TRANSPIRATION  AND  GROWTH. 


119 


daily  evaporation,  which  was  only  8.4  c.  c.  per  day,  in  contrast  to  a  normal 
daily  loss  of  20  to  30  c.  c.  during  this  portion  of  the  growing-season  (table  41). 

Transpiration  and  Increase  in  Leaf- are  a. 

The  behavior  of  plants  of  the  four  species  with  respect  to  water-loss  and 
increase  in  area  during  the  control  period  of  two  weeks  at  Lincoln  is  exhibited 
in  table  41. 

Conditions  and  Results  at  Phillipsburg. 

Installation. 

Plants  of  the  same  species  as  those  used  in  the  preceding  experiment  were 
grown  at  Lincoln  and  shipped  to  the  mixed-prairie  station  at  Phillipsburg, 
where  they  were  used  experimentally  for  the  14-day  period  from  June  18  to 
July  3.  Some  differences  in  the  age  and  size  of  the  various  species  from  those 
at  Lincoln  were  brought  about  by  more  or  less  favorable  growing  conditions 
during  the  few  weeks  preceding  the  beginning  of  the  experiments,  but  the 
several  species  were  as  nearly  as  possible  comparable  with  those  previously 
used.  The  same  methods  were  employed  in  both  cases. 

Physical  Factors. 

The  period  June  19  to  July  3  was  one  of  fairly  typical  weather  for  early 
summer  at  this  station,  when  compared  with  that  of  the  three  preceding  years 
for  which  factor  data  were  obtained.  Eight  days  were  clear,  except  for  a  few 
floating  clouds,  and  the  sun  shone  on  four  others  for  over  half  of  the  time. 
Two  days  alone  were  sufficiently  cloudy  so  that  the  sun  shone  for  less  than  one- 
third  of  the  day.  Heavy  showers  occurred  at  night  on  June  18,  21,  26,  and  29, 
as  well  as  during  the  day  on  June  21,  when  it  was  necessary  to  cover  the 
plants  for  2  hours.  Three  days  were  so  extremely  hot,  windy,  and  dry  that 
it  was  desirable  to  shade  the  plants  and  protect  them  from  the  wind  for 
periods  of  2  to  5  hours.  Notwithstanding  an  adequate  holard,  partial  wilting 
occurred  at  these  times,  crop  and  ruderal  plants  suffering  likewise.  During 
one  of  the  most  severe  days  (June  24)  the  temperature  was  98°  F.  and  the 
humidity  42  per  cent,  while  a  south  wind  of  20  to  30  miles  per  hour  was  blow¬ 
ing.  The  air-temperature  during  the  first  five  days  of  the  period  ranged  from 
65°  to  98°  F.  and  the  humidity  from  41  to  97  per  cent.  For  the  remainder 
of  the  time  the  variations  were  from  42°  to  90°  F.  and  34  to  100  per  cent  humid¬ 
ity.  The  average  day  temperature  for  the  period  was  80.6°  F.  and  the 
average  day  humidity  60  per  cent.  Soil  temperatures  at  a  depth  of  6  inches 
varied  from  74°  to  82°  F. 

The  total  wind  movement  at  a  height  of  39  cm.  during  the  14-day  period 
was  1,100  miles,  an  average  of  3.3  miles  per  hour;  moreover,  most  of  this 
occurred  during  the  day.  The  somewhat  xerophytic  conditions  are  indicated 
by  the  average  daily  evaporation  of  25.5  c.  c.  Under  these  conditions  of 
prevailingly  clear,  warm  weather,  growth  was  marked  and  the  losses  by 
transpiration  were  high  (table  42). 

Conditions  and  Results  at  Burlington. 

Installation. 

The  plants  used  at  Burlington  were  also  grown  in  appropriate  containers  at 
Lincoln  for  the  usual  period  and  shipped  to  Burlington,  where  they  were  used 


120 


PHYTOMETRIC  RESULTS 


experimentally  for  the  14-day  period  from  July  6  to  20.  Methods  similar  to 
those  utilized  for  the  other  stations  were  employed  throughout.  Owing  to  the 
abundance  of  grasshoppers,  it  was  necessary  to  screen  the  inclosure,  a  fence  of 
hardware  cloth  about  4  feet  high,  the  top  edge  of  which  was  turned  outward 
and  downward,  being  employed.  This  modified  the  conditions  of  wind  and 
evaporation  within  to  a  considerable  extent  and  shaded  the  plants  for  about  2 
hours  each  day. 


Transpiration  and  Increase  in  Leaf- are  a. 

Table  42. — Water-loss  and  growth  at  Phillipsburg. 
Helianthus  annuus. 


GQ 

S 

.. 

^  3 
3 

Water  added  (grams). 

"d 

<D 

CO 

3 

u. i 

<D  • 

0 

a 

a 

•  H 

Con- 

-g  2 

c3  X 

0)  A 

c3  G" 

Average  area 

(sq.  cm.). 

'■o 

cr  . 

02 

o 

GO 

c3 

tainer. 

is  ^ 

ca  2 

a 

HH 

June 

23. 

June 

26. 

June 

30. 

July 

2. 

£  M 

*  >> 
i  i  1  l— -H 

c3  3 

•  S 

E 

Total  wa 
(grams 

Initial  ar 
(sq.  cr 

Final  are 

(sq.  cn 

Loss  per 

(grams 

P.  ct.  inc 

area. 

1 

6,862 

50 

200 

300 

200 

6,627 

• 

985 

65.89 

860.86 

463.38 

212 

1,206.5 

2 

6,974 

50 

200 

300 

200 

6,639 

1,085 

52.84 

925 . 73 

489.29 

222 

1,651.9 

3 

7,030 

50 

200 

300 

200 

6,724 

1,056 

57.11 

934.08 

495.59 

213 

1,535.6 

4 

7,036 

50 

200 

300 

200 

6,628 

1,158 

53.75 

727 . 39 

390.57 

296 

1,253.3 

5 

7,061 

50 

200 

300 

200 

6,797 

1,014 

54.91 

870.29 

462.60 

219 

1,484.9 

6 

7,058 

50 

200 

300 

200 

6,718 

1,090 

51.29 

960.98 

506.14 

215 

1,773.6 

7 

7,045 

50 

200 

300 

200 

6,760 

1,035 

50.39 

945.36 

497.88 

208 

1,776.1 

8 

7,074 

50 

300 

400 

200 

6,717 

1,307 

91.86 

1,133.60 

612.73 

213 

1,134.0 

Aver.  .  . 

225 

1,476.9 

Avena  sativa. 

1 

8, 3S8 

200 

350 

400 

200 

8,138 

1,400 

316.37 

1,254.24 

785.31 

178 

296.4 

2 

8,385 

150 

350 

300 

200 

8,210 

1,175 

260.54 

905.84 

583.19 

201 

247.6 

3 

8,442 

200 

350 

400 

200 

8,200 

1,392 

353 . 59 

1,297. 50 

825.55 

169 

266.9 

4 

8,121 

100 

350 

300 

200 

8,053 

1,018 

353.59 

836. 16 

594.88 

171 

136.4 

5 

8,369 

200 

350 

400 

200 

8,129 

1,390 

353.59 

1,239.82 

796.71 

174 

250.6 

6 

8,211 

100 

350 

400 

200 

7,958 

1,303 

316.37 

1,196.56 

756.47 

172 

278.2 

Aver . 

178 

246.0 

Elymus 

CANADENSIS. 

1 

5,048 

100 

200 

200 

4,900 

648 

214.08 

720.90 

467.49 

139 

236.7 

2 

5,289 

200 

400 

300 

4,939 

1,250 

214.08 

780.54 

497.31 

251 

264.6 

3 

5,422 

100 

300 

100 

5,172 

750 

214.08 

763.50 

488.79 

153 

256.6 

4 

Check. . . . 

5,291 

4,741 

200 

400 

300 

4,913 

4,733 

1,278 

8 

214. OS 

789 . 06 

501.57 

255 

268.6 

Aver . 

199 

256.6 

Acer 

NEGUNDO. 

1 

6,190 

200 

100 

6,068 

422 

128.94 

336 . 70 

232.82 

181 

161.1 

2 

6,079 

... 

100 

50 

5,979 

250 

77.52 

214.99 

146.26 

171 

177.3 

3 

4,337 

50 

100 

100 

4,208 

379 

139.28 

393.41 

266.35 

142 

182.5 

4 

4,349 

50 

100 

100 

4,260 

339 

124.81 

285.53 

205.17 

165 

128.8 

5 

6,022 

.  .  . 

100 

,  .  , 

5,956 

166 

59.17 

157.24 

108.21 

153 

165.7 

G 

5,955 

100 

5,878 

177 

69.38 

179.46 

124.42 

142 

158.6 

Aver . 

159 

162.3 

TRANSPIRATION  AND  GROWTH. 


121 


Physical  Factors. 

The  weather  conditions  for  the  first  four  days  of  the  experiment  were  very 
characteristic  of  the  high  plains  during  July,  with  day  temperatures  reaching 
90°  to  96°  F.  and  falling  to  60°  or  65°  F.  at  night,  while  the  humidity  ranged 
from  25  to  30  per  cent  in  the  afternoon  to  80  or  85  per  cent  at  night.  However, 
this  was  followed  by  10  days  during  which  the  atmosphere  was  more  humid 
and  cooler,  due  largely  to  an  unusual  amount  of  cloudy  weather  and  rain. 
Rains  fell  in  the  evening  or  at  night  as  follows:  July  11,  0.02  inch.;  14th, 
1.48  inches;  16th,  0.51  inch;  17th,  0.58  inch.  Moreover,  the  heavy  rains 
were  general  and  greatly  increased  the  humidity.  One  day  was  entirely 
cloudy,  and  four  were  cloudy  half  or  more  of  the  time,  while  on  3  others  the 
sky  was  overcast  more  than  one-fourth  of  the  time,  only  6  days  being  clear. 
With  the  exception  of  the  first  4  days,  clouds  invariably  obscured  the  sun  after 
5  or  6  p.  m. 

The  temperature  ranged  rather  uniformly  between  55°  to  60°  and  80°  to  85° 
F.,  and  the  humidity  usually  reached  100  per  cent  at  night  (the  vegetation 
being  covered  with  rain  or  dew)  and  fell  to  50  to  55  per  cent  during  the  after¬ 
noon  (on  one  day  to  36  per  cent).  The  average  day  temperature  and  humidity 
for  the  period  from  8  a.  m.  to  6  p.  m.  were  80°  and  57  per  cent  respectively. 
While  the  temperature  was  nearly  the  same  as  the  average  day  temperature 
for  the  same  period  during  the  three  preceding  years,  as  determined  by 
hygrothermographs  in  the  field,  the  humidity  was  11  per  cent  higher.  The 
soil  temperature  at  a  depth  of  6  inches  among  the  containers  was  73°  to  86°  F. 

The  wind  movement  at  a  height  of  39  cm.  during  the  first  4  days  averaged 
over  7  miles  per  hour,  but  for  the  rest  of  the  time  it  was  much  less  (3.4  miles 
per  hour).  The  average  daily  evaporation  was  35.4  c.  c.,  which  was  5  c.  c. 
lower  than  for  the  same  period  of  the  preceding  years.  It  was  necessary  to 
shade  the  plants  for  an  hour  or  so  to  prevent  wilting  during  the  first  day 
or  two. 


Transpiration  and  Increase  in  Area. 

Table  43. — Water-loss  and  growth  at  Burlington. 
Helianthus  anntjus. 


Con¬ 

tain¬ 

er. 

Initial  weight, 

July  6  (grams). 

Water  added  (grams). 

Final  weight, 

July  20  (grams). 

Total  water  used 
(grams). 

Initial  area 
(sq.  cm.). 

Final  area 
(sq.  cm.). 

Average  area 
(sq.  cm.). 

Loss  per  sq.  dm. 
(grams). 

P.  ct.  increase  in 
area. 

July 

11. 

July 

13. 

July 

16. 

July 

18. 

July 

19. 

1 

6,526 

100 

100 

300 

300 

300 

6,444 

1,182 

30.62 

1,235.16 

632.89 

187 

3,933.9 

2 

7,572 

100 

100 

300 

300 

300 

7,637 

1,035 

22.22 

775.20 

398.71 

259 

3,388.7 

3 

6,591 

100 

100 

300 

300 

300 

6,409 

1,182 

29.59 

1,159.44 

594.52 

199 

3,818.4 

4 

7,538 

100 

0 

300 

300 

300 

7,617 

921 

21.58 

650.91 

336.25 

274 

2,916.2 

5 

7,599 

100 

0 

300 

300 

300 

7,612 

987 

20.20 

802.33 

411.27 

240 

3,871.7 

6 

6,600 

100 

100 

300 

300 

300 

6,517 

1,183 

26.10 

1,314.35 

670.23 

176 

4,935.8 

7 

6,692 

100 

100 

300 

300 

300 

6,522 

1,270 

21.91 

1,354.01 

687.96 

185 

6,079.9 

8 

7,545 

100 

100 

300 

300 

300 

7,500 

1,145 

27.78 

868.16 

447.97 

256 

3,023.7 

9 

6,477 

100 

0 

300 

300 

300 

6,446 

1,031 

28.17 

1,114.18 

571.18 

181 

3,855.2 

10 

6,636 

100 

0 

300 

300 

300 

6,754 

882 

18.22 

955.05 

486.64 

181 

5,141.7 

Aver 

214 

4,096.5 

122 


PHYTOMETRIC  RESULTS 


Table  43. — Water-loss  and  growth  at  Burlington — Continued 


Avena  sativa. 


Container. 

Initial  weight, 

July  6  (grams). 

Water  added  (grams). 

Final  weight, 

July  19  (grams). 

Total  water  used 

(grams) . 

Initial  area 

(sq.  cm.) 

j 

Final  area 

(sq.  cm.). 

Average  area 

(sq.  cm.). 

Loss  per  sq.  dm. 

(grams) . 

P.  ct.  increase  in 

area. 

July 

11. 

July 

13. 

July 

16. 

July 

18. 

1 

8,850 

200 

250 

200 

8,722 

778 

92.92 

566.94 

329.93 

236 

510.1 

2 

8,732 

150 

100 

200 

150 

8,593 

739 

100.33 

721.32 

410.83 

180 

618.9 

3 

8,702 

150 

100 

200 

200 

8,583 

769 

85.48 

642.81 

364.15 

211 

652.0 

4 

8,803 

100 

100 

150 

100 

8,734 

519 

38.93 

506. 17 

272.55 

190 

1,200.0 

5 

8,915 

150 

100 

200 

200 

8,816 

749 

89.21 

523.91 

306.56 

244 

487.3 

Check . 

8,742 

8,734 

8 

. 

. 

Average . 

212 

693.7 

Elymus  canadensis. 


Initial  weight, 

July  6  (grams). 

Water  added  (grams). 

/•—N 

CO 

a 

"d 

<D 

a 

a 

Container. 

July 

11. 

July 

13. 

July 

16. 

July 

18. 

Final  weight, 
July  20  (gra 

Total  water  us 
(grams) . 

Initial  area 
(sq.  cm.). 

Final  area 
(sq.  cm.). 

Average  area 
(sq.  cm.). 

Loss  per  sq.  di 
(grams) . 

P.  ct.  increase 
area. 

1 

5,253 

100 

0 

50 

5,211 

192 

47.10 

176.87 

111.98 

172 

275.5 

2 

5,277 

•  .  • 

100 

100 

50 

5,226 

301 

88.81 

212.08 

150.45 

200 

138.8 

3 

5,197 

•  .  • 

100 

50 

50 

5,159 

238 

64.98 

155.25 

110.12 

216 

138.9 

4 

5,158 

... 

100 

100 

50 

5,110 

298 

74.18 

175.53 

124.86 

239 

136.6 

5 

5,336 

100 

50 

50 

5,284 

252 

59.15 

132.02 

95.58 

264 

123.2 

Average . 

218 

162  6 

Acer  negundo. 


Container. 

Initial  weight, 

July  5  (grams). 

Water  added  (grams). 

Final  weight, 

July  19  (grams). 

Total  water  used 
(grams). 

Initial  area 
(sq.  cm.). 

Final  area 
(sq.  cm.). 

Average  area 
(sq.  cm.). 

Loss  per  sq.  dm. 
(grams) . 

P.  ct.  increase  in 
area. 

July 

9. 

July 

13. 

July 

16. 

July 

18. 

1 

6,112 

100 

0 

150 

50 

6,055 

357 

134.50 

375.84 

255.17 

139 

179.4 

2 

5,995 

0 

100 

50 

50 

5,986 

209 

70.54 

234.11 

157.33 

137 

231.8 

3 

4,384 

150 

0 

150 

100 

4,300 

484 

163.83 

584.06 

373.95 

129 

256.5 

4 

4,339 

200 

100 

150 

150 

4,252 

687 

283.08 

737.99 

510.54 

134 

160.7 

5 

4,355 

150 

100 

150 

150 

4,290 

615 

218.84 

685.40 

452.12 

136 

213.2 

6 

4,194 

100 

100 

100 

100 

4,151 

443 

125.58 

475.71 

300.65 

147 

278.8 

Average . 

137 

220.1 

TRANSPIRATION  AND  GROWTH. 


123 


Table  44. — Transpiration  and  growth  at  the  stations. 


Species. 

Water-loss  per 
sq.  dm.  (grams). 

Increase  in  area 
(p.  ct.). 

Rate  of  growth,  based 
on  actual  increase  in 
area  (p.  ct.). 

Lin¬ 

coln. 

Phil¬ 

lips¬ 

burg. 

Bur¬ 

ling¬ 

ton. 

Lin¬ 

coln. 

Phil¬ 

lips¬ 

burg. 

Bur¬ 

ling¬ 

ton. 

Lin¬ 

coln. 

Phil¬ 

lips¬ 

burg. 

Bur¬ 

ling¬ 

ton. 

Sunflower . 

145 

225 

214 

409 

1,477 

4,097 

854 

860 

998 

Wild  rye . 

72 

199 

218 

239 

257 

163 

410 

549 

140 

Oats . 

99 

178 

212 

279 

246 

694 

1,155 

796 

510 

Box-elder . 

85 

159 

137 

85 

162 

220 

52 

161 

370 

Average.  .  . 

100 

190 

195 

253 

535 

1,294 

618 

591 

504 

Table  45. — Environmental  conditions  at  the  stations. 


Station. 

Approxi¬ 

mate 

hours 

sunshine. 

Average 

day 

temp. 

(°  F.). 

Soil 

temp. 

(°  F.) 

Average 

day 

humidity 
(p.  ct.). 

Average 
daily  evap¬ 
oration 
(c.  c.). 

Wind 
per  hour 
(miles). 

Lincoln . 

39 

70.1 

62  to  71 

75 

8.4 

3.6 

Phillipsburg . 

75 

80.6 

74  82 

60 

25.5 

3.3 

Burlington . 

71 

80.0 

73  86 

57 

35.4 

3.4! 

Summary  and  Conclusions. 

This  onerous  series  proved  a  disappointment  in  so  far  as  normal  climatic 
relations  were  concerned,  owing  to  the  wholly  exceptional  weather.  This  is 
revealed  by  table  45,  and  is  brought  out  even  more  graphically  by  comparing 
the  data  here  with  those  obtained  during  other  years.  The  amount  of  sun¬ 
shine  at  Lincoln  was  little  more  than  half  that  at  the  other  stations,  while  the 
air-temperature  averaged  10°  lower  and  the  soil  temperature  ranged  from  11° 
to  15°  lower.  The  average  humidity  was  15  to  18  per  cent  higher  and  the 
evaporation  but  a  third  or  a  fourth  of  that  at  Phillipsburg  or  Burlington. 
Hence,  it  is  easy  to  understand  why  the  increase  in  area  was  twice  as 
great  at  Phillipsburg  and  more  than  four  times  as  great  at  Burlington 
ihough  the  normal  relation  is  suggested  by  the  rate  of  growth  based  on  the 
actual  increase  in  area  and  by  the  order  of  water-loss  at  the  three  stations. 
Thus,  while  the  plant  responses  are  in  agreement  with  the  physical  factors  for 
the  respective  fortnights  concerned,  it  is  obvious  that  entirely  comparable 
results  could  be  insured  only  by  dealing  with  the  growth  season  for  each  species. 
An  adequate  record  of  transpiration  and  growth  for  such  a  period  at  stations 
widely  separated  demands  at  least  one  resident  investigator  for  each  station, 
and  such  studies  must  await  the  future. 

TRANSPIRATION  AND  GROWTH  OF  COMMUNITIES. 

Transpiration  from  Natural  Cover  and  Crops. 

Objectives. 

One  of  the  major  tasks  of  quantitative  ecology  is  to  determine  the  functional 
responses  of  plants  when  grouped  in  communities.  While  much  light  can  be 
obtained  by  the  use  of  individual  plants  under  control  in  the  field,  in  the  form 


124 


PHYTOMETKIC  RESULTS. 


of  standard  phytometers,  these  differ  essentially  in  their  soil  and  competition 
relations  from  plants  growing  together  in  the  actual  cover.  Hence,  the  task 
is  to  maintain  these  natural  relations  of  the  community  and  at  the  same  time  to 
secure  a  degree  of  control  that  modifies  the  efficient  factors  little  or  not  at  all. 
In  the  case  of  transpiration,  for  example,  these  requisites  can  be  met 
only  by  weighing,  as  all  other  methods  modify  the  physical  factors  to  an 
undesirable  degree.  The  method  that  maintains  the  soil  and  community 
relations  with  the  minimum  disturbance  is  the  soil-block,  which  was  first 
employed  for  determining  the  chresard  in  the  field  (Clements,  1904,  1905). 
This  requires  only  such  slight  modifications  as  those  of  size  and  form  to 
become  applicable  to  all  problems  in  which  an  undisturbed  soil-root  core 
is  indispensable. 

In  consequence,  the  first  objective  was  to  perfect  the  soil-block  method  so 
that  it  could  be  used  in  the  field  with  both  convenience  and  accuracy.  Because 
of  its  importance  in  the  grassland  climate,  the  chief  function  to  be  measured 
was  transpiration,  though  chresard  and  aeration  can  be  studied  with  something 
of  the  same  readiness.  In  the  present  case  the  transpiration  from  representa¬ 
tive  cores  was  followed  in  the  proper  climate  of  each  association,  but  it  is 
evident  that  the  containers  can  be  moved  or  exchanged  between  different 
edaphic  or  climatic  stations  and  thus  serve  as  reciprocal  phytometers.  This 
permits  the  determination  of  the  transpiration  behavior  of  each  climax  in  its 
own  climate  in  terms  of  adjustment  and  adaptation  and  at  the  same  time 
affords  a  basis  for  comparing  adjacent  climaxes.  A  further  use  of  funda¬ 
mental  value  arises  out  of  the  rainfall  relation.  The  method  of  the  soil-core 
not  only  makes  it  possible  to  trace  the  complete  water-cycle  of  rainfall,  holard, 
evaporation,  and  transpiration,  but  also  to  estimate  the  extent  to  which  the 
vegetation  of  each  region  may  furnish  the  water- vapor  for  its  own  rainfall 
(Clements,  1923).  Finally,  it  also  opens  up  a  new  field  in  the  functional  rela¬ 
tion  of  roots  to  the  soil  as  an  actual  structure,  which  shows  striking  differences 
from  climate  to  climate,  as  well  as  from  one  local  habitat  to  another. 

Methods. 

A  steel  cylinder  12  inches  tall  and  with  an  inner  area  of  1  square  foot,  the 
lower  edge  of  which  was  sharpened,  was  driven  into  the  grassland  soil  to  a 
depth  of  4  inches.  Care  was  taken  to  cut  off  none  of  the  leaves  belonging  to 
the  plants  in  the  square  foot  selected,  which  was  chosen  with  a  special  regard 
to  its  representative  structure.  The  cylinder  was  then  carefully  removed, 
leaving  the  column  of  soil  intact,  and  replaced  by  one  of  heavy  galvanized 
iron  3  feet  long  and  reinforced  at  both  ends  by  a  heavy  wire  over  which  the 
metal  was  turned  back  smoothly.  After  starting  a  row  of  these  cylinders  at 
distances  of  8  inches,  a  trench  2  feet  wide  was  dug  around  them  to  a  depth  of 
over  3  feet.  In  this  process  no  soil  was  removed  within  3  or  4  inches  of  the 
cylinder.  As  the  trench  was  deepened,  the  columns  of  soil  were  carefully 
pared  away  with  large  knives  in  such  a  manner  that  the  cylinders  could  be 
forced  down  under  considerable  pressure  from  above.  By  shaping  the  column 
for  a  few  inches  in  front  of  the  descending  cylinder,  it  was  possible  to  force 
the  latter  into  place  over  a  tightly  fitting  soil-core  to  a  depth  of  3  feet.  The 
columns  were  then  undercut  and  smoothed  off  level  with  the  lower  end  of  the 
cylinder.  A  loose-fitting  metal  bottom  with  the  edges  2  inches  deep  was 


TRANSPIRATION  FROM  NATURAL  COVER  AND  CROPS.  125 


placed  over  the  end  and  the  entire  container  was  then  weighed  on  a  portable 
Fairbanks  scale  sensitive  to  one-fourth  pound. 

In  the  meantime,  a  trench  sufficiently  wide  and  deep  to  receive  the  cylinders 
in  an  upright  position  had  been  dug  in  a  nearby  area,  care  being  taken  not  to 
cover  the  grass  with  soil.  The  containers  were  lowered  in  the  new  trench  and 
slid  into  place  on  a  plank  in  the  bottom,  after  which  the  bottoms  were  made 
water-tight  by  means  of  a  measured  amount  of  hot  wax  of  the  usual  composi¬ 
tion.  The  trench  was  then  filled  with  soil  and  pieces  of  sod  were  fitted  around 
the  tops  so  that  the  surface  conditions  would  be  essentially  normal.  The 
trenches  were  selected  so  that  the  surface  water  would  readily  drain  away 
from  them  and  in  addition  the  plants  were  covered  by  wooden  roofs  whenever 
rain  was  actually  falling.  This  was  imperative  because  of  the  varying  inter¬ 
ception  of  rainfall  by  the  different  vegetation  in  the  several  containers.  In 
the  case  of  the  cultivated  crops,  oats  and  millet,  the  usual  type  of  bottom  was 
replaced  by  one  3  feet  deep,  owing  to  the  difficulty  of  selecting  a  proper  slope 
for  drainage.  In  order  to  determine  the  amount  of  water  evaporated  from 
the  cultivated  soil,  the  plants  were  removed  from  one  container  in  each  field. 
In  another  check,  the  natural  grasses  were  left  in  place  after  having  been 
killed  by  the  addition  of  a  measured  amount  of  boiling  water. 

From  time  to  time,  depending  upon  the  weather  and  the  needs  of  the  plants, 
water  in  measured  amounts  was  slowly  added  to  all  the  containers,  and  as  a 
result  there  was  little  shrinkage  of  the  core  from  the  sides  of  the  container. 
None  of  the  plants  died,  and  even  those  near  the  edges  gave  no  signs  of  wilting, 
demonstrating  that  the  roots  in  the  core  supplied  abundant  water  for  trans¬ 
piration.  Much  care  was  exercised  in  watering,  so  that  there  was  little  or  no 
run-off  down  the  sides  of  the  core.  This  was  accomplished  by  pouring  the 
water  on  slowly  and  pressing  the  moist  soil  firmly  against  the  cylinder  wherever 
the  contact  was  not  complete.  At  the  end  of  the  period  the  containers  were 
again  weighed  and  the  losses  calculated. 

At  the  end  of  the  experiment  the  vegetation  was  carefully  removed  at  the 
soil  surface  by  means  of  a  hand  grass-clipper.  The  dense  foliage  of  former 
years  was  carefully  separated  from  the  living  plants,  the  latter  oven-dried  at 
60°  C.,  and  weighed. 

True  Prairie,  Series  1. 

Installation. — The  first  series  consisted  of  6  sod-cores  which  were  installed 
on  the  high  prairie  during  the  period  of  May  31  to  June  15.  The  group  in 
container  2  consisted  chiefly  of  a  sod  of  Andropogon  nutans  and  Bouteloua 
racemosa ,  in  which  were  found  4  bunches  of  Koeleria  cristata.  Container  1 
was  very  similar,  having  been  taken  within  18  inches  from  the  former;  the 
plants  in  it  were  killed  with  hot  water  and  it  was  then  employed  as  a  control. 
The  third  group  consisted  mainly  of  Andropogon  nutans,  A.  scoparius,  and 
Koeleria,  and  container  4  resembled  it  closely.  The  group  in  container  5 
comprised  several  bunches  of  Stipa  spartea,  4  small  clumps  of  Bouteloua 
racemosa,  and  3  of  Andropogon  scoparius;  No.  6  was  occupied  chiefly  by 
Stipa  spartea  and  Andropogon  scoparius. 

The  entire  period  was  exceptionally  cool  and  wet,  only  one  day  being  wholly 
sunny  and  the  total  sunshine  being  approximately  only  a  third  of  the  total 
daytime  period.  The  average  day  temperature  was  70°  F.  and  the  day 


126 


PHYTOMETRIC  RESULTS. 


humidity  75  per  cent.  The  unusual  nature  of  the  weather  is  perhaps  best 
revealed  by  the  fact  that  the  average  daily  evaporation  was  only  8.4  c.  c.  in 
contrast  with  a  normal  loss  of  20  to  30  c.  c.  per  day  during  this  period. 

Results. — A  striking  character  of  the  soil  columns  is  their  rather  uniform 
weight.  Cores  1  to  4  were  obtained  from  a  single  trench,  the  extreme  distance 
between  the  containers  not  exceeding  6  feet.  The  weight  of  the  3  cubic  feet  of 
soil  (exclusive  of  container)  varied  only  from  289  to  295  pounds.  Soil  columns 
5  and  6  were  obtained  about  50  feet  distant  from  the  first  trench. 


Table  46. — Water-losses  from  sods  in  high  prairie,  Lincoln,  Nebraska. 


Container. 

Original 
weight, 
May  31. 

Weight 

of 

seal. 

Water 
added 
May  31. 

Final 
weight, 
June  15. 

Loss. 

Dry 

weight  of 
foliage. 

Loss  per 
gram  of  dry 
weight. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

gm. 

gm. 

1  (control) . 

309  50 

0.60 

5.5 

312.5 

3.1 

2 . . 

307.00 

0.60 

4.0 

303.0 

8.6 

19.18 

203.4 

3 . 

305.25 

1.20 

4.0 

302.0 

8.45 

18.95 

202.3 

4 . 

303.75 

1.00 

4.0 

302.5 

6.25 

13.88 

204.3 

5 . 

313.00 

0.80 

4.0 

311.0 

6.8 

18.95 

162.8 

6 . 

308.00 

1.20 

4.0 

308.0 

5.2 

15.18 

155.4 

The  water-losses,  though  low,  are  fairly  consistent,  ranging  from  2.1  to  5.5 
pounds  per  square  foot  in  excess  of  that  of  the  area  covered  with  dead  grasses. 
Moreover,  the  variations  are  directly  proportional  to  the  extent  of  the  grassy 
cover,  as  expressed  in  dry  weight.  The  mixture  of  grasses  (chiefly  andropogons 
and  Koeleria )  lost  about  203  grams  of  water  per  gram  of  dry  matter,  which 
was  somewhat  more  than  that  from  Stipa  spartea  (average  159  grams). 

True  Prairie,  Series  2. 

Installation. — Because  of  the  unfavorable  conditions  during  the  first  series, 
the  experiment  was  repeated  from  July  24  to  August  8,  5  containers  being 
installed  on  the  high  prairie  and  4  in  the  adjoining  low  prairie.  In  container 
1  a  mixture  of  Andropogon  nutans ,  Koeleria  cristata,  and  Poa  pratensis,  with 
a  single  plant  of  Amorpha  canescens  (. Andropogon  being  most  abundant), 
covered  half  of  the  area.  These  had  an  average  height  of  12  inches.  The 
surface  of  three-fourths  of  the  second  container  was  covered  principally  with 
Andropogon  nutans ,  but  also  with  a  mixture  of  Koeleria  cristata,  Bouteloua 
racemosa,  and  a  little  Poa  pratensis,  with  an  average  height  of  15  inches. 
The  grasses  in  container  3  were  chiefly  Andropogon  scoparius,  with  a  third  as 
much  A.  nutans  and  a  very  little  Bouteloua  racemosa ;  the  height  was  14  inches. 
In  container  4,  one-fifth  only  of  the  area  was  bare,  the  rest  being  occupied 
with  a  mixture  of  the  grasses  named  above,  Andropogon  scoparius  dominating. 
Amorpha  canescens  and  Antennaria  campestris  were  each  represented  by  a 
single  small  clump.  The  control  container,  No.  5,  in  which  the  grasses  were 
killed  as  usual,  was  very  similar  to  No.  3. 

In  the  low  prairie  two  clumps  of  Andropogon  furcatus,  22  inches  in  average 
height,  occupied  slightly  less  than  half  of  the  area  in  container  6,  the  rest  being 
bare.  Nearly  two-thirds  of  the  area  in  container  7  was  bare,  the  rest  being 
occupied  by  a  large  clump  of  A.  furcatus  16  inches  in  height.  Spartina  cyno- 


TRANSPIRATION  FROM  NATURAL  COVER  AND  CROPS.  127 


suroides  and  a  little  Panicum  virgatum,  with  an  average  height  of  38  inches, 
filled  about  one-third  of  container  8,  the  remainder  being  destitute  of  plants. 
The  remaining  cylinder  was  sunk  and  a  soil-core  obtained  in  a  field  of  alfalfa 
where  the  plants  were  21  inches  high  and  beginning  to  blossom  freely.  A 
single  clump  in  the  center  of  the  core  was  obtained  which  occupied  only 
one-fourth  of  the  area. 

Because  of  a  prolonged  period  of  hot,  dry  weather,  the  grasses  at  both  sta¬ 
tions  had  rolled  leaves  and  some  of  them  wilted  during  the  afternoons,  a 
result  rarely  seen  in  the  true  prairie.  However,  the  weather  conditions  for 
the  following  15  days  were  below  normal  in  the  amount  of  sunshine  and  heat. 
Only  2  days  were  entirely  clear  and  rain  fell  on  8  different  days.  The  average 
day  temperature  was  79°  F.  and  the  average  day  humidity  was  80  per  cent. 
With  respect  to  transpiration,  conditions  were  much  more  nearly  normal 
than  in  the  preceding  series,  as  is  shown  by  the  fact  that  the  average  daily 
evaporation  was  22  c.  c.  in  contrast  to  8  c.  c. 

Results. — The  losses  per  square  foot  in  the  upland  prairie  ranged  from  9.4  to 
13.7  pounds,  as  compared  with  4.8  pounds  from  the  control.  In  the  low  prairie 
the  losses  varied  from  12.3  to  17.5  pounds,  owing  to  the  more  luxuriant  growth 
of  the  vegetation,  while  that  from  alfalfa  was  21.5  pounds.  Based  on  the 
quantity  of  water  lost  per  dry  weight,  the  upland  prairie  grasses  show  a 
relatively  higher  loss  (maximum  332.5  gm.)  than  the  coarser,  larger-stemmed 
lowland  species,  where  a  maximum  loss  of  only  165  gm.  of  water  per  gram  of 
dry  matter  was  found.  On  this  basis  the  woody-stemmed  Spartina  transpired 
less  even  than  the  upland  grasses.  Alfalfa  lost  442  grams  of  water  per  gram 
of  dry  matter. 

Table  47. — Water-losses  from  sods  and  from  alfalfa ,  Lincoln,  Nebraska. 


Container. 

Original 
weight 
July  24. 

Weight 

of 

seal. 

Water  added. 

Final 
weight 
Aug.  8. 

Loss. 

Dry 

weight 

of 

plants. 

Water 
lost  per 
gram  dry 
weight  of 
plants. 

July 

25. 

July 

26. 

July 

28. 

July 

30. 

Aug. 

1. 

Aug. 

3. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs.' 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

gm. 

gm. 

1 . 

294.75 

0.61 

2 

2 

3 

3 

2 

2 

300 

9.36 

12.77 

332.5 

2 . 

294 . 50 

1.22 

2 

2 

3 

3 

2 

2 

296.0 

13.72 

32.07 

194.1 

3 . 

291.25 

1.08 

2 

2 

3 

3 

2 

2 

295.0 

11.33 

23.12 

222.3 

4 . 

286.25 

0.81 

2 

2 

3 

3 

2 

2 

291.25 

9.81 

22.70 

196.0 

fo.hp.AkT 

293  75 

0.81 

4 

2 

1 

3 

1 

0 

300.75 

4.81 

6 . 

308.75 

2.03 

5 

4 

5 

2 

2 

2 

313.25 

17.53 

66.53 

119.5 

7 . 

291.00 

0.81 

5 

4 

5 

2 

2 

2 

296.5 

15.31 

42.17 

164.7 

8 . 

322.00 

2.03 

5 

4 

5 

2 

2 

2 

331.75 

12.28 

56.07 

99.4 

9 . 

307.50 

2.03 

5 

7 

5 

3 

2 

2 

312.0 

21.53 

22.09 

442.1 

Mixed  Prairie. 

Installation. — At  Phillipsburg  6  cylinders  were  used  in  the  mixed  prairie 
and  3  in  an  adjoining  field  of  oats.  Container  2  was  two-thirds  occupied  by  a 
dense  sod  of  Bouteloua  gracilis  with  a  very  little  pistillate  Bulbilis  dactyloides ; 
these  had  an  average  height  of  9  inches.  The  third  container  was  fully  two- 
thirds  covered  by  a  practically  pure  growth  of  Bouteloua  gracilis  with  an 
average  height  of  9  inches,  in  which  were  found  a  few  stalks  of  Sporobolus 
cryptandrus  and  one  small  Callirrhoe  involucrata.  The  control,  No.  1,  bore  a 
vegetative  cover  of  a  kind  and  density  almost  exactly  like  that  in  No.  3. 


128 


PHYTOMETRIC  RESULTS. 


About  one-fourth  of  the  area  in  container  4  was  bare;  the  rest  was  covered  with 
a  dense  sod  of  pistillate  Bulbilis  dactyloides  4  to  8  in.  tall.  There  were  also 
four  small  clumps  of  Car  ex  filifolia  and  a  very  small  amount  of  Bouteloua 
gracilis.  A  fine  clump  of  Andropogon  furcatus,  18  inches  in  average  height, 
occupied  96  square  inches  of  the  area  in  container  5,  the  rest  being  devoid  of 
vegetation.  Container  6  also  bore  a  clump  of  the  same  grass  91  square  inches 
in  extent  at  the  base  and  with  an  average  height  of  20  inches. 

The  period  from  June  18  to  July  3  was  typical  of  early  summer  at  this 
station,  as  shown  by  the  factor  data  for  the  preceding  years.  Except  for  a 
few  clouds,  9  days  were  clear  and  4  others  were  sunny  for  more  than  half  of 
the  time.  The  average  day  temperature  was  80.6°  F.  and  the  average  day 
humidity  was  60  per  cent.  The  effect  of  the  factors  concerned  in  transpiration 
is  indicated  by  the  average  daily  evaporation,  which  was  25.5  c.  c. 

Results. — Among  the  short-grasses  the  amount  of  water  added  slightly 
exceeded  the  amount  used;  it  was  approximately  the  same  in  amount  in  the 
oats,  but  the  soil  lost  3  to  7  pounds  of  its  original  weight  in  the  case  of  the 
bluestems.  The  losses  from  the  control  with  a  dead  short-grass  cover  and 
from  bare  soil  were  4.4  and  7.2  pounds  respectively.  Those  from  containers 
2  and  3,  where  the  dominants  were  grama  grass,  were  14.7  and  16.2  pounds 
per  square  foot  respectively,  or  approximately  1  pound  (pint)  of  water  per 
day.  The  buffalo-grass  sod  lost  nearly  as  much,  14.2  pounds,  while  loss 
from  the  big  bluestem  was  nearly  twice  as  great,  27  and  28  pounds  respectively. 
The  oats,  even  in  the  late  stage  of  development,  lost  practically  the  same 
amount  of  water  as  the  short-grasses  (14.7  and  16.4  pounds). 


Table  48. — Water-losses  from  sods  and  oats ,  Phillipsburg,  Kansas. 


Con¬ 

tain¬ 

er. 

Dominant 

species. 

Origi¬ 

nal 

weight, 
June  18. 

Weight 

of 

seal. 

Water  added. 

Final 
weight, 
July  3. 

Loss. 

Dry 

weight 

of 

plants. 

Loss 

per 

gram 
of  dry 
weight. 

.Tune 

18. 

June 

19. 

June 

22. 

June 

26. 

June 

30. 

1 

Control,  dead 

Bouteloua  gra- 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

am. 

Qm. 

cilis . 

276 . 25 

0.9 

7 

0 

1 

2 

4 

286.75 

4.40 

2 

B.  gracilis .... 

278.75 

0.9 

2 

2 

4 

4 

4 

281.00 

14.65 

19.30 

344.3 

3 

Do . 

274.00 

1.2 

2 

2 

4 

4 

4 

275.00 

16.20 

20.42 

359.9 

4 

Bulbilis  dacty- 

loides . 

275.50 

0.75 

2 

2 

4 

4 

4 

278.00 

14.25 

21.76 

297.0 

5 

Andropogon 

furcatus . 

282.50 

0.9 

2 

2 

4 

4 

4 

271.25 

28.15 

53.90 

236.9 

6 

Do . 

282.30 

0.75 

2 

2 

4 

7 

4 

275.00 

27.05 

53.94 

227.5 

7 

Oats . 

269.25 

2.43 

0 

2 

4 

4 

4 

271.00 

14.68 

34.30 

194.1 

8 

Do  .  .  .. 

267.50 

2.43 

0 

2 

4 

4 

4 

267.5 

16.43 

36.43 

204.6 

9 

Control,  bare 

soil . 

285.75 

2.43 

0 

2 

1 

2 

2 

288.00 

7.18 

. .  . . 

•  .  • 

Short-grass  Plains. 

Installation. — The  experiments  in  the  short-grass  plains  were  carried  out 
at  Burlington  from  July  5  to  20.  Six  containers  were  used  in  the  grassland 
and  three  in  an  adjoining  field  of  millet.  Container  2  was  covered  with  a 
dense  closed  mat  of  nearly  pure  pistillate  Bulbilis  dactyloides,  except  for  about 
one-sixth  of  Bouteloua  gracilis.  This  formed  a  fine  green  carpet  4  inches  in 
height.  Only  one-fifth  of  the  area  inclosed  by  the  cylinder  was  bare.  The 
check  container,  No.  1,  in  which  the  vegetation  was  killed,  was  similar,  except 


TRANSPIRATION  FROM  NATURAL  COVER  AND  CROPS.  129 


that  one-fourth  of  the  area  was  bare.  Container  3  was  very  much  like  No.  1, 
except  for  a  mixture  of  about  one-third  grama,  which  was  flowering  at  a 
height  of  8  inches.  The  average  height  of  the  short-grass  foliage  was  4.5 
inches.  Container  4  consisted  of  nearly  pure  pistillate  Bulbilis  about  4  inches 
tall,  with  just  a  little  grama,  some  of  which  had  flower-stalks;  only  one-sixth 
of  the  area  was  bare.  Containers  5  and  6  had  a  rather  dense  growth  of  Agro~ 
pyrum  glaucum.  The  foliage  averaged  20  inches  in  height,  most  of  the  stems 
being  dry  and  yellowish  to  a  height  of  6  or  8  inches.  There  were  no  flower- 
stalks.  The  two  containers  were  very  similar,  No.  6  having  slightly  less 
vegetation.  The  millet  was  about  4  weeks  old,  of  thick  stand,  and  had  an 
average  height  of  18  inches.  It  had  not  begun  to  head  at  the  beginning  of  the 
experiment  (July  5),  but  by  the  end  of  the  15-day  period  it  was  well  headed 
at  an  average  height  of  20  inches.  Two  containers  with  millet  were  used,  and 
one  from  which  the  crop  had  been  removed  by  pulling  out  the  plants. 

The  weather  during  the  period  was  rather  exceptional  for  July  on  the  high 
plains,  only  7  of  the  15  days  being  entirely  clear.  The  average  day  tem¬ 
perature  was  80°  F.  and  the  average  day  humidity  was  57  per  cent.  While  the 
temperature  was  much  the  same  as  that  for  this  period  during  the  3  preceding 
years,  the  humidity  was  11  per  cent  higher.  The  average  daily  evaporation 
was  35.4  c.  c.  as  compared  with  40.5  c.  c.  for  the  same  period  in  previous 
years. 


Table  49. — Water-losses  from  sods  and  millet,  Burlington,  Colorado. 


Con¬ 

tain¬ 

er. 

Dominant 

species. 

Origi¬ 

nal 

weight, 
July  5. 

Weight 

of 

seal. 

Water  added,  July— 

Final 
weight, 
July  20. 

r 

Loss. 

Dry 

weight 

of 

plant. 

Loss 
per 
gram 
of  dry 
weight 

5. 

6. 

7. 

8. 

9. 

12. 

17. 

18. 

19. 

1 

Control, 

dead 

Buffalo 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

gm. 

gm. 

grass. . . . 

254.75 

2  03 

5 

0 

0 

2 

0 

3 

3 

0 

1 

265.75 

5.03 

2 

Same,  living 

260.5 

1.22 

2 

2 

0 

3 

0 

3 

3 

0 

2 

264.25 

12.47 

15.4 

367.3 

3 

Do... 

254 

1.22 

2 

2 

0 

3 

0 

3 

3 

0 

2 

259.00 

11.22 

17.75 

286.7 

4 

Do. . . 

265.25 

1.22 

2 

2 

0 

3 

0 

3 

3 

0 

2 

268.75 

12.72 

15.75 

366.3 

5 

Wheat 

grass. . . . 

251.5 

1.22 

4 

2 

2 

3 

0 

4 

3 

0 

2 

254.00 

18.72 

45.31 

187.4 

6 

Do... 

254.25 

1.08 

4 

2 

2 

3 

0 

4 

3 

0 

2 

258.50 

16.83 

40.32 

189.3 

7 

Millet . 

274 . 78 

1.22 

0 

2 

2 

3 

2 

3 

3 

3 

2 

274.50 

21.50 

46.95 

207.7 

8 

Do.  .  . 

278.75 

1.22 

0 

2 

2 

3 

0 

3 

3 

3 

2 

279.00 

18.97 

40.20 

214.2 

9 

Control 

bare  soil. 

267.25 

1.22 

0 

1 

1 

2 

0 

3 

3 

0 

0 

271.50 

6.97 

. 

•  •  *  * 

Results. — The  final  weights  of  the  containers  were  only  slightly  greater  than 
their  original  weights,  which  means  that  approximately  all  of  the  water  added 
was  again  lost  by  transpiration  or  direct  evaporation  from  the  soil  and  dead 
plant  surfaces.  The  latter  amount  was  only  5.03  pounds  (container  1).  The 
square  foot  of  Bulbilis  and  Bouteloua  in  each  of  the  three  containers  lost  11  to 
13  pounds.  The  wheat-grasses  lost  17  to  19  pounds,  varying  directly  with  the 
amount  of  foliage  concerned,  while  the  losses  from  the  millet  were  even  greater, 
19  to  21.5  pounds.  It  is  interesting  to  note  that  the  bare  area  lost  approxi¬ 
mately  2  pounds  more  water  than  a  similar  area  covered  with  dead  grasses. 
The  loss  of  water  in  grams  per  gram  of  dry  weight  of  the  vegetation  is  almost 
identical  (about  366  grams)  in  containers  2  and  4,  the  smaller  ratio  in  No.  3 


130 


PHYTOMETRIC  RESULTS. 


probably  being  due  to  the  presence  of  flower-stalks  of  grama  grass,  which 
increased  the  dry  weight  but  transpired  little.  The  relatively  low  ratio  of  the 
wheat-grasses  (188  grams)  may  readily  be  explained  when  their  large,  very 
fibrous  stems  are  considered.  Losses  from  the  millet  were  intermediate, 
probably  being  relatively  less  than  earlier  because  of  the  heads. 

Considered  solely  on  the  basis  of  loss  per  square  foot,  the  millet  ranks  first, 
wheat-grass  second,  and  the  short-grasses  last.  Thus,  as  is  shown  by  the  dis¬ 
tribution  of  the  native  species,  wheat-grass  is  less  adapted  to  this  semiarid 
region  than  are  the  short-grasses,  more  than  one-third  more  water  escaping 
from  the  area  occupied  by  the  former.  These  data,  however,  hold  only  for 
the  conditions  of  the  experiment,  viz,  with  the  plants  growing  in  very  dry  soil 
and  under  unusual  humidity  for  the  Great  Plains.  This  is  clearly  brought  out 
by  a  comparison  of  the  physical  factors  writh  those  of  preceding  seasons. 

Summary. 

Transpiration  from  natural  cover. — As  in  the  case  of  water-loss  from  the 
phytometers,  the  exceptional  weather  of  the  summer  obscured  the  normal 
climatic  response  of  the  sod-cores.  When  the  physical  factors  and  the  type  of 
vegetation  are  taken  into  account  (table  50),  it  is  clear  why  the  low  short-grass 
cover  at  Burlington  in  the  driest  climate  transpired  less  than  the  mixed  prairie 
at  Phillipsburg  in  a  moister  atmosphere,  and  more  than  the  luxuriant  true 
prairie  at  Lincoln  in  a  much  more  humid  climate.  Thus  again,  while  the  use  of 
sod-cores  contributed  no  clear-cut  evidence  as  to  the  relation  of  the  three 
climaxes  and  their  climates,  it  does  demonstrate  the  value  of  the  method  and 
what  can  be  expected  of  it  when  employed  through  a  series  of  years.  The 
losses  from  the  three  crops,  while  of  interest,  have  no  comparative  value,  since 
a  different  species  was  used  at  each  station;  they  are  distinctly  helpful,  how¬ 
ever,  in  showing  the  similarity  in  the  behavior  of  the  native  cover  and  repre¬ 
sentative  crops  for  each  station  and  in  potential  importance  for  the  rainfall  of 
each  region.  However,  in  the  future  development  of  the  method  it  is  obvious 
that  the  same  dominant  and  the  same  crop  should  be  employed  throughout 
the  series  of  stations,  and  this  should  involve  the  reciprocal  transfer  of  sod- 
cores  and  crop-cores  between  the  three  stations. 


Table  50. — Comparison  of  factors  and  average  water-loss. 


Station. 

Dominant 

grasses. 

Date  of 
experi¬ 
ment. 

Approx¬ 

imate 

sun¬ 

shine. 

Average 

day 

temper- 

ture. 

Average 

day 

humid¬ 

ity. 

Average 

daily 

evapo¬ 

ration. 

Average 
daily  loss 
from 
sq.  ft. 
of  cover. 

Bulbilis . 

July  5 
to 

July  20 

]  p.  ct. 

\  71 

J 

0  F. 

p.  ct. 

57 

c.  c. 

lbs. 

Burlington .... 

•j  Bouteloua .  . .  > 
w  Agropyrum .  .  ( 

80 

35.4 

0.96 

Phillipsburg. .  . 

( Bouteloua.  . .  . 

June  18 

\Andropogon.  . 

July  3 

75 

80.6 

60 

25.5 

1.33 

Lincoln . 

Andropogon. ) 
Stipa . 1 

July  24 

r 

79 

80 

22.0 

0.8.5 

|  Koeleria . 

Bouteloua .  . . 

to 

Au&.  8 

CLIP-QUADRATS. 


131 


Growth  of  Natural  Cover  and  Crops. 

Objectives. 

The  growth  of  a  representative  area  of  a  community  may  be  used  as  a 
climatic  index  as  well  as  a  measure  of  response  in  much  the  same  way  as 
transpiration.  It  possesses  three  distinct  advantages  over  the  latter,  though 
the  two  are  complementary  and  hence  one  can  not  replace  the  other.  Growth 
demands  no  laborious  installation,  as  it  can  be  determined  directly  from  the 
native  or  culture  community  in  position.  While  it  can  be  measured  at  any 
time,  it  yields  the  major  values  at  the  end  of  the  growing-season,  and  thus 
does  not  require  the  services  of  a  resident  investigator.  Moreover,  it  inte¬ 
grates  the  response  for  the  whole  season,  though  as  a  complex  it  permits  less 
ready  analysis  than  transpiration  and  is  also  less  satisfactory  for  short 
periods.  In  short,  it  is  the  simplest  and  most  convenient  of  all  community 
phytometers  when  employed  in  the  form  of  the  clip-quadrat.  This  is  the 
only  practicable  method,  as  the  measurement  of  the  individuals  in  a  com¬ 
munity  group  is  too  time-consuming  to  be  desirable.  There  are  certain  cases 
in  which  it  is  profitable  to  pull  the  individuals  out  with  their  roots,  but  this  is 
hardly  feasible  in  a  close  cover  or  a  compact  soil.  The  clip-quadrat  is  merely 
the  usual  one  of  a  square  meter  in  extent,  from  which  the  shoots  are  cut  at  any 
desired  time.  It  may  be  either  smaller  or  larger  in  order  to  meet  special  con¬ 
ditions,  as  in  the  case  of  crops  planted  in  rows.  The  growth  is  regularly 
expressed  in  terms  of  dry  matter,  but  in  the  case  of  grazing  ranges  or  forage 
crops,  the  green  weight  should  likewise  be  found.  Finally,  the  clip-quadrat 
facilitates  the  analysis  of  community  response  to  climatic  factors  by  making  it 
possible  to  measure  growth  during  different  portions  of  the  season  or  its 
variations  from  season  to  season  or  from  the  wet  to  the  dry  phase  of  a  climatic 
cycle,  and  to  determine  the  part  played  by  the  various  species  in  the  total 
production. 

In  the  case  of  the  grains,  it  is  often  preferable  to  select  the  individuals  to  be 
cut  in  accordance  with  the  results  desired,  instead  of  taking  all  those  in  a 
particular  area  (Weaver,  Jean,  and  Crist,  1922).  This  may  be  regarded  as  an 
aggregate  clip-quadrat;  it  has  the  further  advantage  of  permitting  measure¬ 
ment  of  particular  individuals  throughout  the  season. 

Plan. 

Clip-quadrats  were  first  installed  at  the  three  stations  in  1920;  these  repre¬ 
sented  high  and  low  prairie  in  the  true-prairie  association,  mixed  prairie,  and 
short-grass  plains.  They  were  again  cut  in  1921  and  1922  to  determine  the 
fluctuation  from  year  to  year.  The  first  step  in  the  simple  procedure  was  to 
select  a  considerable  number  of  quadrats  in  typical  areas  of  each  climax. 
The  height  and  density  of  the  cover,  the  abundance  of  dominant  and  sub¬ 
dominant  species,  the  presence  of  layers,  etc.,  were  recorded  and  photographs 
made  of  certain  of  the  quadrats.  In  some  instances  it  has  proved  desirable 
to  make  a  chart  of  these  as  well.  The  cover  was  then  removed  by  cutting  it 
near  the  surface  and  at  a  uniform  level  with  a  hand-clipper.  It  was  collected, 
sorted,  and  then  shipped  into  the  laboratory  to  be  thoroughly  air-dried,  after 
which  the  actual  production  was  determined  on  the  basis  of  the  dry  weight. 
This  gave  an  expression  of  the  growth  of  the  community  as  a  unit,  as  well  as 
the  role  taken  by  each  dominant  or  subdominant  in  this.  As  complete  factor 


132 


PHYTOMETRIC  RESULTS. 


records  were  obtained  at  each  station,  this  made  it  possible  to  correlate  the 
yield  of  community  or  species  with  the  climate  and  the  season  at  each.  The 
physical  factors  for  the  several  years  have  been  given  in  the  preceding  chapters 
and  hence  are  not  repeated  here. 

Since  even  the  most  uniform  cover  shows  some  variation  in  density,  the 
clip-quadrats  were  selected  with  much  care  and  in  sufficient  number  to  insure 
dependable  results.  As  in  all  ecological  studies  that  are  adequate,  i.  e.,  causal 
and  quantitative,  rather  than  merely  mathematical,  this  demands  considerable 
knowledge  of  the  community  and  can  not  be  met  by  random  selection.  The 
best  plan  is  to  locate  a  proper  proportion  of  quadrats  in  pure  or  nearly  pure 
stands  of  each  dominant  whenever  these  are  present  and  to  distribute  the 
others  among  the  various  mixtures.  It  is  often  desirable  to  take  the  sub¬ 
dominants  into  account  in  doing  this,  as  their  yield  may  be  much  greater  than 
that  of  the  grasses. 

Results  for  1920. 

The  growth  response  for  this  year  was  obtained  from  about  400  clip- 
quadrats,  of  which  50  were  in  the  true  prairie  at  Lincoln,  50  from  mixed  prairie 
at  Phillipsburg,  50  from  the  short-grass  plains  at  Burlington,  and  30  from  each 
of  the  cultivated  fields  at  the  various  stations.  The  short-grasses  at  Burling¬ 
ton  averaged  103  gm.,  those  at  Phillipsburg  290  gm.  Wheat-grass  ( Agropyrum 
glaucum)  at  Burlington  yielded  398  gm.  per  square  meter,  while  at  Phillipsburg 
the  yield  was  480  gm.  A  mixture  of  short-grass  and  tail-grasses  gave  244  gm. 
per  square  meter  at  Burlington  and  470  gm.  at  Phillipsburg,  and  the  mixed 
prairies  at  Phillipsburg  produced  a  total  yield  of  439  gm.  per  square  meter, 
while  those  at  Lincoln  averaged  452  gm.  The  average  yield  at  Phillipsburg 
(439  gm.)  exceeded  that  from  the  hilltops  at  Lincoln  (361  gm.)  or  even  the 
slopes  (429  gm.)  at  this  time  (July  9),  but  did  not  equal  that  of  the  lowland, 
which  was  564  gm.  Moreover,  an  examination  of  the  factor  data  shows  that 
late-summer  drought  usually  prevails  at  the  western  stations  and  good  plant 
growth  is  not  maintained.  This  is  well  illustrated  by  a  second  series  of 
quadrats  cut  August  16  to  24.  The  average  yield  at  Burlington  was  196  gm. 
(more  mixed  short  and  tall  grass  quadrats  being  included  than  before),  at 
Phillipsburg  310  gm.,  and  at  Lincoln  465  gm.  On  the  basis  of  the  50  quadrats 
taken  at  each  station  during  the  season,  the  average  total  production,  pro¬ 
ceeding  from  the  drier  western  station  eastward,  was  183,  378,  and  458  gm. 
respectively. 

Crops  of  oats  ( Avena  sativa),  spring  wheat  ( Triticum  aestivum),  barley 
{Hordeum  vulgare),  alfalfa  ( Medicago  sativa),  and  white  sweet  clover  ( Melilotus 
alba)  were  grown  in  plats  adjoining  the  several  grassland  stations  (Weaver, 
Jean,  and  Crist,  1922:76).  Each  kind  of  crop  was  planted  from  the  same  lot 
of  seed  and  grown  under  conditions  of  farm  practice  common  to  the  several 
localities  respectively.  The  crop  plants  were  thoroughly  air-dried  before 
weighing,  and  the  relative  height  of  the  mature  oats  and  wheat  at  the  several 
stations,  as  well  as  the  comparative  yield  from  an  average  square  meter,  were 
determined.  The  yield  is  the  average  of  25  to  30  square-meter  quadrats  taken 
from  each  of  the  several  plats  at  the  three  stations  when  the  grain  was  ripe. 
400  plants  of  alfalfa  and  300  of  sweet  clover  of  average  size  were  carefully 
selected  at  each  of  the  stations,  cut  at  the  ground-line,  thoroughly  air-dried, 
and  the  dry  weight  ascertained.  This  was  done  during  July  and  again  in 


GROWTH  OF  NATURAL  COVER  AND  CROPS. 


133 


August  for  the  sake  of  obtaining  comparative  values  between  clip-quadrats 
and  a  group  of  selected  plants  (table  51). 

The  height-growth  of  all  crops  was  greatest  at  Lincoln,  less  at  Phillipsburg, 
and  least  at  Burlington,  the  height  of  the  former  averaging  more  than  twice 
that  of  the  latter.  The  maximum  penetration  of  roots  was  usually  greatest  at 
Phillipsburg,  next  at  Lincoln,  and  least  at  Burlington,  a  divergence  readily 
explained  by  the  greater  holard  at  the  first  and  the  dry  subsoil  and  hard-pan 
at  the  last. 


Table  51. — Growth  and  yield  of  crop-quadrats  and  plants,  1920. 


Crop  and  station. 

Date  of 
harvest. 

Average 

height. 

Maximum 
depth  of 
roots. 

Average 
yield  in 
grams  per 
sq.  met^r. 

Weight 
of  1,000 
kernels. 

Oats: 

Lincoln . 

July 

12 

feet. 

3.0 

feet. 

4.8 

706 

gm. 

20.1 

Phillipsburg . 

July 

20 

2.6 

6.0 

379 

16.6 

Burlington . 

July 

19 

1.5 

2.7 

175 

16.2 

Wheat : 

Lincoln . 

July 

15 

3.2 

4.8 

740 

29.8 

Phillipsburg . 

July 

20 

2.3 

5.8 

322 

9.1 

Burlington . 

July 

19 

1.7 

2.7 

205 

20.1 

Barley: 

Lincoln . 

July 

12 

2.7 

5.4 

607 

32.7 

Phillipsburg . 

July 

17 

2.4 

6.7 

407 

14.7 

Burlington . 

July 

19 

1.7 

2.9 

176 

23.9 

Alfalfa: 

Lincoln . 

July 

12 

1.5 

5.7 

Dry  weight 
of  plants. 
528 

Phillipsburg . 

July 

9 

0.7 

5.0 

292 

Burlington . 

July 

8 

0.4 

2.3 

122 

Sweet  clover: 

Lincoln . 

July 

12 

2.0 

5.5 

840 

Phillipsburg . 

July 

9 

1.3 

5.7 

461 

Burlington . 

July 

8 

0.4 

2.8 

213 

Alfalfa: 

Lincoln . 

Aug. 

9 

1.8 

5.9 

739 

Phillipsburg . 

Aug. 

4 

1.2 

•  •  • 

601 

Burlington . 

Aug. 

5 

0.6 

2.0 

214 

Sweet  clover: 

Lincoln . 

Aug. 

9 

2.5 

•  •  • 

1,103 

Phillipsburg . 

Aug. 

4 

1.7 

•  •  • 

869 

Burlington . 

Aug. 

5 

0.8 

2.7 

323 

The  average  yield  of  grain  for  the  three  cereals  was  about  twice  as  much  at 
Lincoln  as  at  Phillipsburg,  and  nearly  twice  as  much  at  the  latter  as  for 
Burlington.  A  similar  relation  obtained  for  the  first  cutting  of  alfalfa  and 
sweet-clover,  but  at  the  second  cutting  Phillipsburg  more  nearly  approached 
Lincoln.  Thus,  the  five  crops  decreased  decisively  in  both  height  and  yield 
from  Lincoln  westward  in  correspondence  with  the  rainfall,  holard,  and 
humidity. 

Results  for  1921. 

Two  series  of  cuttings  were  made  during  1921,  one  about  July  1  and  a  second 
during  the  last  half  of  August.  Ten  clip-quadrats  each  of  Bulbilis  dactyloides 
and  Agropyrum  glaucum  were  used  at  each  of  the  stations  early  in  the  summer; 
at  all  of  these  both  grasses  had  headed  or  blossomed  at  the  time  of  cutting. 


134 


PHYTOMETRIC  RESULTS. 


The  buffalo-grass  averaged  about  4.5  inches  high  at  Burlington,  while  the 
staminate  spikes  were  5.5  inches  tall.  In  the  mixed-prairie  the  foliage  of  this 
grass  averaged  5  inches  in  height  and  the  flower-stalks  6  inches.  Bulbilis 
occurs  in  the  prairies  at  Lincoln  only  where  the  tail-grasses  are  held  in  check  by 
grazing ;  hence  it  was  impossible  to  secure  an  ungrazed  sod  comparable  to  that 
at  the  other  stations.  The  foliage  was  only  4.5  inches  high  and  the  effects  of 
heavy  overgrazing  the  preceding  year  were  apparent.  On  July  1  the  average 
yield  of  10  quadrats  at  each  of  the  respective  stations  was  207,  266,  and  235 
gm.  per  square  meter.  At  Burlington  the  leaves  of  wheat-grass  had  reached  an 
average  height  of  16  inches  and  the  flower-stalks  of  26  inches  at  this  time, 
at  Phillipsburg  the  respective  values  were  22  and  30  inches,  and  at  Lincoln  24 
and  32  inches.  The  average  yield  of  10  quadrats  from  each  station  was  400, 
457,  and  606  gm.  respectively. 


Table  52. — Growth  and  yield  of  crop-quadrats  in  1921. 


Crop  and  station. 

Aver¬ 

age 

height. 

Average 
number 
stalks 
per  sq. 
meter. 

Average 

number 

stalks 

per 

plant. 

Average 
length 
heads  or 
panicles 
in  inches. 

Average 
number 
heads  per 
sq. 

meter. 

Average 

total 

weight  dry 
matter  per 
sq.  meter. 

Maxi¬ 

mum 

depth. 

Oats: 

feet. 

gm. 

feet. 

Lincoln . 

3.2 

375 

3.3 

10.5 

283 

792 

4.8 

Phillipsburg.  .  . 

2.8 

353 

2.9 

9 

269 

366 

5.3 

Burlington .... 

1.5 

414 

2.5 

5 

171 

180 

2.5 

Wheat: 

Lincoln . 

3.2 

648 

2.8 

4 

365 

557 

4.3 

Phillipsburg.  .  . 

2.6 

475 

1.8 

3.5 

211 

314 

4.5 

Burlington .... 

1.6 

419 

1.6 

2.5 

277 

172 

2.5 

Barley: 

Lincoln . 

3.1 

384 

3.7 

3.5 

306 

622 

4.6 

Phillipsburg.  .  . 

2.8 

253 

2.2 

3.25 

201 

369 

6.0 

Burlington .... 

1.3 

255 

1.6 

2 

197 

122 

2.5 

On  August  17,  12  quadrats  cut  in  the  high  prairie  at  Lincoln  yielded  an 
average  of  581  gm.,  and  a  similar  number  from  the  low  prairie  929  gm.,  giving 
an  average  yield  of  755  gm.  This  considerably  exceeded  the  average  weight 
of  11  tail-grass  quadrats  cut  on  August  30  at  Phillipsburg,  which  was  477  gm. 
The  average  of  the  44  quadrats  from  both  cuttings  at  each  station  was  as 
follows:  Burlington  353  gm.,  Phillipsburg  402  gm.,  and  Lincoln  603  gm.  per 
square  meter. 

Crops  of  the  smaller  cereals  were  again  grown  in  1921  under  conditions 
similar  to  those  already  described  for  1920. 

There  was  a  regular  decrease  in  height  of  the  crop  from  the  more  humid  to 
the  more  arid  stations.  The  same  general  relation  holds  for  the  average 
number  of  stalks  per  square  meter,  except  at  Burlington,  where  many  tiny 
stalks  only  2  to  4  inches  tall  started  growth  relatively  early  and  soon  dried  out, 
but  remained  until  harvest.  During  1920  the  average  number  of  stalks  per 
square  meter  at  Burlington  was  from  one-third  to  one-half  less  than  at  the 
other  stations,  although  the  number  at  Phillipsburg  often  exceeded  that  at 
Lincoln.  The  average  number  of  stalks  per  plant  (1921)  was  in  direct  relation 
to  the  water-content  of  soil  and  other  factors  favorable  or  unfavorable  to  plant 
growth.  In  general,  this  relation  held  also  during  1920.  The  average  number 


GROWTH  OF  NATURAL  COVER  AND  CROPS. 


135 


of  heads  per  square  meter  and  the  average  length  of  heads  or  panicles  de¬ 
creased  from  Lincoln  to  Phillipsburg  to  Burlington  respectively.  An  exception 
to  this  occurred  in  the  case  of  the  number  of  heads  of  wheat  at  Burlington 
when  compared  with  Phillipsburg,  while  the  difference  in  this  respect  in  the 
case  of  barley  was  small.  However,  a  clear  gradation  in  the  reduction  of  total 
dry  weight  from  east  to  west  is  apparent,  giving  a  direct  correlation  with 
differences  in  water-content  and  humidity. 

Results  for  1922. 

A  single  series  of  cut  quadrats  was  obtained  in  1922;  these  were  taken  on 
August  4  to  15,  beginning  with  the  short-grass  plains.  A  series  of  7  quadrats 
of  Bulbilis  at  Burlington  yielded  an  average  of  179  gm.,  while  the  average  of  a 
similar  series  at  Phillipsburg  was  260  gm.  A  series  of  mixed  short  and  tall 
grass  cuttings  at  these  two  stations  yielded  263  and  365  gm.  respectively.  The 
differences  in  the  height-growth  of  foliage  and  flower-stalks  for  both  kinds  of 
grasses  were  again  like  those  recorded  for  the  preceding  years.  A  series  of  8 
representative  quadrats  of  wheat-grass  was  also  obtained  at  both  Phillips¬ 
burg  and  Lincoln.  The  average  height  of  the  foliage  and  flower-stalks  re¬ 
spectively  was  15  and  26  inches  at  the  former  station,  and  17  and  30  inches  at 
the  latter.  The  respective  yields  were  334  and  541  gm.  per  square  meter.  A 
series  of  27  quadrats  containing  mixed  tail-grasses,  largely  Andropogon 
scoparius,  A.  furcatus,  and  A.  nutans,  was  secured  from  these  two  stations. 
Repeated  measurements  showed  that  the  average  height  of  the  general  level 
of  the  foliage  was  3  to  8  inches  greater  at  Lincoln  (13  to  24  inches  tall)  than 
in  the  mixed  prairie.  The  yield  in  grams  per  square  meter  was  287  and  413 
at  the  two  stations  respectively.  The  average  yield  of  all  the  quadrats  for 
this  year  in  the  three  grassland  communities  was  224,  311,  and  447  gm.  at 
Burlington,  Phillipsburg,  and  Lincoln  respectively. 


Table  53. — Growth  and  yield  of  crop-quadrats,  1923. 


Crop  and  station. 

Date  of 
harvest. 

Height. 

Dry ' 
weight.1 

Oats: 

in. 

gm. 

Lincoln . 

July 

7 

42 

2,637.0 

Phillipsburg. .  . 

July 

3 

32 

905.0 

Burlington .... 

July 

7 

18 

806.5 

Wheat: 

Lincoln . 

July 

7 

42 

2,395.0 

Phillipsburg.  .  . 

July 

3 

29 

1,296.0 

Burlington .... 

July 

7 

24 

801.5 

Barley: 

Lincoln . 

July 

2 

43 

1,671.5 

Phillipsburg. .  . 

July 

3 

37 

1,292.5 

Burlington .... 

July 

7 

26 

1,038.5 

1  Total  of  straw  and  grain. 


Five  fields  of  maize  were  selected  as  representative  of  conditions  about  each 
of  the  three  stations  respectively,  all  of  which  were  within  a  radius  of  2  miles  of 
the  stations  at  which  holard  and  other  factor  determinations  were  made.  10 
stalks  were  then  selected  from  various  places  in  the  field  and  the  measure¬ 
ments  recorded.  The  seventh  leaf  was  selected  for  measurements  of  length  and 
width.  After  completing  the  measurements  on  each  stalk,  the  ear  was  husked 


136 


PHYTOMETRIC  RESULTS. 


and  placed  in  a  sack,  10  ears  being  secured  from  each  field.  Finally,  a  typical 
stalk,  as  determined  by  the  measurements  of  the  10  preceding,  was  selected, 
cut  off  at  the  ground  line,  cut  into  pieces,  and  after  removing  the  ear  but  not 
the  husks,  was  placed  in  another  sack.  These  sacks  were  kept  well  ventilated, 
and  after  all  had  become  thoroughly  air-dried  the  weight  of  their  contents 
was  ascertained.  Consistent  and  marked  increases  in  height  and  diameter  of 
stalk,  height  of  ear,  number  and  length  of  leaves,  length  and  diameter  of  ear, 
as  well  as  dry  weight  of  stalks  and  ears,  were  found  proceeding  from  west  to 
east.  The  respective  values  for  average  weight  of  stalk  and  weight  of  ear  were 
320  and  82  gm.  for  Burlington,  413  and  110  gm.  for  Phillipsburg,  and  496  and 
183  gm.  for  Lincoln. 

Results  for  1923. 

No  clip-quadrats  were  taken  from  native  vegetation  in  1923,  but  three  were 
made  in  plats  of  each  of  the  grains  at  the  three  stations. 

As  in  previous  years,  there  was  a  pronounced  decrease  in  the  height  of  all 
three  species  from  Lincoln  westward,  the  plants  at  Burlington  averaging 
about  half  as  tall  as  at  Lincoln.  With  respect  to  weight,  the  differences  were 
even  greater,  oats  and  wheat  yielding  a  third  as  much  as  at  Lincoln.  The 
average  production  for  the  three  crops  was  2,234  gm.  at  Lincoln,  1,164  gm. 
at  Phillipsburg,  and  882  gm.  at  Burlington,  in  close  correspondence  with  rain¬ 
fall,  evaporation,  and  chresard. 


Table  54. — Average  yield  of  clip-quadrats  in  grams. 


1920. 

1921. 

1922. 

Dominant  type 
of  vegetation. 

Lin¬ 

coln. 

Phil¬ 

lips¬ 

burg. 

Bur¬ 

ling¬ 

ton. 

Lin¬ 

coln. 

Phil¬ 

lips¬ 

burg. 

Bur¬ 

ling¬ 

ton. 

Lin¬ 

coln. 

Phil¬ 

lips¬ 

burg. 

Bur¬ 

ling¬ 

ton. 

Buffalo-grass . 

290 

98 

235 

266 

207 

260 

179 

Wheat-grass . 

•  •  • 

541 

500 

606 

457 

400 

541 

334 

•  •  • 

Mixed  short  and  tall 

grasses . 

•  •  • 

313 

197 

•  .  • 

•  ■  • 

•  •  • 

•  •  • 

365 

263 

Mixed  tail-grasses . 

458 

410 

755 

477 

413 

287 

Average  (based  on 
number  of  quad- 

rats) . 

458 

378 

183 

603 

402 

353 

447 

311 

224 

Summary. 

In  every  case  each  grass  or  mixture  of  grasses  yielded  progressively  less  as 
the  rainfall  and  holard  decreased  to  the  westward.  The  only  exception  is  the 
case  of  buffalo-grass  at  Lincoln  in  1921,  and  this  has  already  been  explained  as 
an  effect  of  grazing.  Moreover,  the  averages  for  each  year  at  the  several 
stations  show  a  graduated  series,  plant  production  increasing  with  increased 
efficiency  of  rainfall.  However,  it  may  be  readily  seen  that  the  total  yield 
at  all  of  the  stations  was  greater  in  1921  than  during  the  preceding  or  following 
year,  an  increase  particularly  noticeable  in  the  case  of  the  late-maturing  tail- 
grasses. 

It  was  early  determined  that  the  water  relations  of  soil  and  air  were  con¬ 
trolling,  other  factors  being  merely  contributory.  The  yield  of  pure  stands  of 


GROWTH  OF  NATURAL  COVER  AND  CROPS. 


137 


short-grasses  ( Bulbilis  dadyloides  and  Bouteloua  gracilis),  wheat-grass 
( Agropyrum  glaucum),  mixed  short  and  tall  grasses,  and  mixed  tail-grasses 
was  found  to  decrease  from  the  true  prairie  to  short-grass  plains  directly  with 
the  chresard  and  inversely  with  evaporation.  The  same  relation  was  de¬ 
termined  not  only  for  the  smaller  cereals  (oats,  wheat,  and  barley),  but  also 
for  alfalfa  and  sweet  clover,  as  well  as  for  maize.  The  plant  yield  at  each 
station  during  different  seasons  was  closely  correlated  with  the  variations  in 
rainfall  and  holard.  Deficiencies  in  water-content  were  naturally  most  marked 
late  in  the  summer,  and  their  effect  was  especially  to  be  found  in  the  late- 
maturing  tail-grasses  at  the  eastern  stations.  The  results  obtained  with 
crop-plants  were  comparable  in  practically  every  respect,  demonstrating  that 
the  method  was  equally  applicable  to  both  native  and  cultivated  species. 

Structural  Response  of  Dominants  and  Subdominants. 

Scope  and  Significance. 

Comprehensive  studies  have  been  made  of  the  leaf-structure  of  the  great 
majority  of  the  climax  dominants  of  the  grassland,  as  well  as  of  a  considerable 
number  of  serai  dominants,  subdominants,  and  trees.  The  material  was 
obtained  from  both  native  and  experimental  plants,  and  in  the  case  of  the  most 
important  species  represented  the  whole  range  of  adjustment  and  adaptation, 
from  salt-flat  and  swamp  through  low  and  high  prairie  to  gravel-knoll  at 
Lincoln,  and  from  Nebraska  City  to  Lincoln,  Phillipsburg,  Burlington,  and 
Colorado  Springs.  As  was  to  be  expected,  the  grasses  in  general  were  very 
stable  as  to  leaf-structure,  the  adjustment  to  the  several  climates  occurring 
chiefly  in  function  and  growth,  and  hence  in  form.  As  a  rule,  distinct  ecads 
were  produced  only  in  the  series  of  edaphic  stations  with  their  more  efficient 
differences,  and  the  various  species  and  genera  naturally  responded  in  very 
different  degree  even  to  these.  Moreover,  the  effect  of  a  particular  habitat 
tended  to  be  cumulative,  and  greater  changes  will  probably  appear  in  the 
course  of  the  next  few  years.  This  is  suggested  by  the  existing  adaptations 
shown  by  the  leaves  to  the  respective  climates  and  recorded  in  the  growth- 
forms  and  in  the  genera.  With  occasional  exceptions,  the  leaf-structure  is 
essentially  the  same  for  the  dominants  of  each  association,  but  differs  markedly 
from  one  association  to  another.  This  seems  to  be  a  more  recent  adaptation 
that  has  been  impressed  upon  the  earlier  one  characteristic  of  each  genus, 
with  the  consequence  that  it  is  necessary  to  distinguish  three  successive 
changes  of  varying  degree  in  many  dominants.  Furthermore,  this  adapta- 
tional  series  affords  a  new  approach  to  climatic  shifts  in  the  past  and  to  the 
basic  correlation  of  ungulate  teeth  and  hoofs  with  changing  vegetation. 
For  these  reasons,  as  well  as  because  of  the  large  amount  of  material  available, 
it  has  seemed  desirable  to  treat  this  phase  of  the  investigation  in  a  separate 
paper  (Clements,  1924). 


6.  RESUME. 

PLAN  AND  METHODS. 

An  endeavor  has  been  made  to  determine  experimentally  the  factors 
operating  in  the  composition  and  sequence  of  the  climax  grassland  associations 
lying  between  the  Missouri  River  and  the  Rocky  Mountains.  Lincoln, 
Nebraska,  was  selected  as  representative  of  true  prairie,  Phillipsburg,  in 
north-central  Kansas,  of  mixed  prairie,  and  Burlington,  in  eastern  Colorado, 
of  short-grass  plains.  The  altitude  rises  from  1,100  feet  at  Lincoln  to  1,900 
feet  at  Phillipsburg  and  4,160  feet  at  Burlington.  Since  the  associations  are 
zoned  from  east  to  west,  precipitation  is  the  chief  factor  in  determining  the 
type  of  grassland;  it  decreases  through  this  series  of  stations  from  28  through 
23  to  17  inches  annual  mean.  A  fourth  station  was  maintained  in  the  edge  of 
the  subclimax  prairie  at  Nebraska  City,  50  miles  southeast  of  Lincoln,  where 
the  precipitation  is  33  inches.  In  addition  to  these  climatic  stations,  a  series 
of  edaphic  ones  ranging  through  gravel-knoll,  high  prairie,  low  prairie,  salt-flat, 
swamp,  and  cultivated  field  was  maintained  at  Lincoln.  Moreover,  some 
reciprocal  transplants  from  Colorado  Springs,  Colorado;  Tucson,  Arizona; 
and  Berkeley,  California,  were  made  at  several  of  these  stations. 

Continuous  records  of  the  most  important  ecological  factors,  viz,  precipita¬ 
tion,  temperature  of  air  and  soil,  humidity,  and  evaporation,  were  secured  and 
frequent  measurements  were  made  of  the  holard  to  a  depth  of  4  feet,  of  light, 
and  wind  velocity,  in  addition  to  physical  and  chemical  analyses  of  the  soils. 
In  the  endeavor  to  interpret  the  various  climatic  and  edaphic  complexes  in 
terms  of  plant  activities,  seeding  and  transplanting  were  carried  out  in 
different  ways  in  the  several  communities.  Seeds  were  sown  in  the  undis¬ 
turbed  grass  cover,  others  were  placed  in  especially  prepared  trenches,  while 
still  others  were  sown  in  denuded  quadrats.  Seedlings  were  transplanted 
and  reestablished  under  favorable  conditions,  and  finally,  large  blocks  of  sod 
of  mature  plants  were  also  employed.  Some  individuals  were  favored  by 
watering,  while  others  were  exposed  unaided  to  the  test  of  the  new  habitat. 
Frequent  checks  were  applied,  resulting  in  complete  records  of  the  plant’s 
activities.  The  investigation  was  begun  in  1919  and  continued  until  the  close 
of  the  growing-season  in  1923. 

Fruits  and  seeds  of  a  large  variety  of  native  grasses,  forbs,  shrubs,  and  trees 
from  a  wide  range  of  habitats  were  employed.  These  were  kept  dry,  but 
subjected  to  winter  temperatures  at  Lincoln,  Nebraska,  and  the  germinability 
of  the  seeds  was  determined  previous  to  planting,  more  than  60  species  being 
tested.  Great  variability  in  the  vitality  of  the  seeds  from  year  to  year  was 
found,  and  this  could  be  traced  to  differences  in  climate.  A  germination  of 
20  to  25  per  cent  was  exceptional,  while  one  of  10  to  15  per  cent  was  quite 
usual.  Experiments  were  also  made  to  disclose  the  effect  of  depth  of  planting 
upon  germination  and  establishment.  With  most  grasses  a  depth  exceeding 
0.5  to  1  inch  was  detrimental,  and  most  species,  like  the  composites,  did  best 
at  a  depth  of  0.12  to  0.25  inch. 

Surface  sowing  consisted  of  scattering  the  seeds  in  selected  marked  areas 
with  a  typical  cover  of  vegetation,  without  disturbing  the  surface,  and  adding 
only  enough  debris  to  prevent  the  seeds  from  blowing  away.  Upon  germina¬ 
tion  the  seedlings  at  once  met  the  keen  competition  from  the  existing  vegeta- 


138 


PLAN  AND  METHODS. 


139 


tion  for  water  and  nutrients  below  ground  and  for  light  above.  Frequently 
the  latter  was  as  low  as  5  to  10  per  cent,  even  early  in  the  summer.  By 
planting  the  seeds  in  a  trench  4  inches  deep,  for  which  the  sod  had  been  broken, 
the  soil  pulverized,  and  a  good  seed-bed  prepared,  competition  both  above  and 
below  ground  was  removed  for  a  short  time.  Denuded  quadrats  0.5  meter 
square  were  also  employed,  the  native  vegetation  likewise  being  removed  and 
a  good  seed-bed  prepared  to  a  depth  of  4  inches.  This  method  eliminated 
competition  for  light  and  also  for  water  and  nutrients  for  a  time,  but  other 
unfavorable  factors  were  introduced,  such  as  higher  temperatures  and  greater 
evaporation.  To  tide  the  plant  over  the  most  critical  period  in  its  life,  that  of 
ecesis,  the  method  of  seedling  transplants  was  also  employed.  These  were 
grown  in  2.5  to  4  inch  flower  pots  until  they  were  3  or  4  weeks  old,  when  they 
were  transplanted  into  a  specially  prepared  trench  without  disturbing  the 
root  system  and  watered  for  a  period  of  about  10  days.  A  fourth  method,  that 
of  transplanting  mature  perennials,  was  also  utilized.  Blocks  of  sod  10  inches 
square  and  8  inches  deep  were  transplanted  reciprocally  among  most  of  the 
stations,  a  control  block  being  replanted  in  the  area  where  the  species  was 
secured.  As  far  as  possible,  sowing  and  transplanting  were  done  preceding  or 
coincident  with  the  inception  of  new  growth  and  at  a  time  when  the  holard 
was  distinctly  favorable. 

COMMUNITIES. 

The  vegetation  at  each  station  has  been  studied  and  described  in  detail,  in 
connection  with  the  measurement  of  physical  factors.  Ninety  per  cent  of  the 
cover  at  Burlington  ( Bouteloua-Bulbilis  association)  consists  of  closed  mats  of 
short-grasses  (mostly  Bulbilis)  forming  a  carpet  seldom  over  4  inches  deep. 
At  Phillipsburg  ( Bouteloua-Stipa  association)  tail-grasses,  chiefly  Andropogon, 
alternate  with  or  form  a  layer  above  the  shorter  buffalo  and  grama  grasses, 
the  former  reaching  a  height-level  of  14  inches  by  midsummer.  In  the  true 
prairie  ( Stipa-Koeleria  association)  the  vegetation  is  distinctly  of  the  tail- 
grass  sod  type.  The  chief  genera  are  Stipa,  Koeleria,  Andropogon ,  and 
Sporobolus,  with  which  are  associated  subdominants  to  form  extensive 
societies.  By  June  1  the  grasses  have  a  height-level  of  6  or  8  inches  and  the 
upper  story  of  forbs  attains  a  height  of  15  to  22  inches.  The  subclimax  prairie 
at  Nebraska  City  (. Andropogon  associes),  in  addition  to  the  true-prairie 
species  which  grow  somewhat  more  rank,  is  characterized  by  the  regular 
occurrence  of  Andropogon  furcaius  and  Panicum  virgatum  on  highland,  while 
the  various  potential  scrub  societies  usually  held  in  check  by  mowing  and  fire, 
indicate  its  t  rue  relationship  to  forest.  The  low  prairie  at  Lincoln  is  dominated, 
almost  to  the  exclusion  of  other  species,  by  Andropogon  furcatus  and  nutans, 
Panicum  virgatum ,  and  Spartina  cynosuroides,  and  is  actually  an  edaphic 
postclimax  (Plant  Succession,  109),  closely  resembling  the  subclimax  grass¬ 
land.  The  swamp  area  is  covered  by  the  Spartina  consocies  bordered  by  a 
zone  of  Poa  pratensis ,  but  the  bluegrass  has  been  replaced  by  Spartina  during 
the  course  of  the  experiment.  The  vegetation  both  here  and  in  low  prairie 
reaches  a  height  of  4  or  5  feet.  The  salt-flat,  on  an  area  near  the  low  prairie, 
had  just  enough  sodium  chloride,  combined  with  an  unfavorable  soil  structure, 
to  exclude  most  prairie  species,  and  is  occupied  by  an  open  growth  of  Dis- 
tichlis  spicata  and  dwarf  Agropyrum  glaucum ,  seldom  exceeding  5  to  8  inches 


140  RESUME. 

in  height.  The  gravel-knoll  is  covered  with  mats  of  Bouteloua  gracilis  inter¬ 
mixed  with  Bouteloua  hirsuta  and  often  also  with  sparse  tail-grasses  in  the 
intervals.  These  grow  in  porous  sandy  to  gravelly  drift  soil,  which  forms  the 
crest  of  a  steep  slope  to  the  south.  It  is  a  miniature  short-grass  area  of  edaphic 
nature  surrounded  by  true  prairie. 

PHYSICAL  FACTORS  FOR  1920. 

A  comparison  of  the  physical  factors  during  1920  at  the  three  major  climatic 
stations  shows  that  conditions  for  plant-growth  in  respect  to  rainfall,  holard, 
temperature,  humidity,  wind,  and  evaporation  were  most  favorable  at  Lincoln, 
intermediate  at  Phillipsburg,  and  least  favorable  at  Burlington.  These  condi¬ 
tions  are  indicated  by  the  native  vegetation  and  are  borne  out  by  results  of 
these  experiments.  Holard  and  humidity  were  found  to  be  the  controlling 
factors  in  plant  growth,  all  others  being  secondary.  The  precipitation  is  not 
only  5  inches  less  at  Phillipsburg  and  11  inches  less  at  Burlington  than  at 
Lincoln,  but,  owing  to  lighter  showers,  greater  run-off,  and  increased  evapora¬ 
tion,  it  is  also  progressively  less  efficient  westward.  While  at  Lincoln  sufficient 
chresard  was  found  at  all  times  and  at  all  depths  to  4  feet  for  good  growth, 
a  period  of  midsummer  drought  occurred  at  Phillipsburg,  and  at  Burlington 
the  holard  was  favorable  only  until  June  (to  a  depth  of  2  feet  only),  after 
which  marked  deficiencies  were  of  frequent  occurrence.  Evaporation  was 
lowest  at  Lincoln  (9  to  25  c.  c.  daily),  intermediate  at  Phillipsburg  (11  to  32 
c.  c.),  and  highest  at  Burlington  (23  to  60  c.  c.). 

ECESIS  DURING  1920. 

Both  germination  and  establishment  at  the  three  stations  were  in  the 
sequence  of  increasing  water-content.  Germination  by  all  methods  of  planting 
averaged  86,  80,  and  38  per  cent,  and  establishment  42,  33,  and  25  per  cent 
at  Lincoln,  Phillipsburg,  and  Burlington  respectively.  Surface  sowing  gave 
both  the  poorest  germination  and  poorest  establishment,  and  seeding  in 
denuded  quadrats  the  best.  In  most  cases  better  growth  occurred  at  Lincoln 
than  at  the  other  two  stations.  Germination  and  growth  in  cultivated  areas 
adjoining  the  several  grassland  stations  were  much  better  than  in  the  sodded 
areas,  but  the  sequence  of  the  stations  was  the  same. 

In  order  to  more  fully  understand  the  causes  for  the  success  or  failure  of 
seedlings,  the  root  habit  was  studied  both  in  native  grassland  and  in  cultivated 
soil.  During  1918,  when  seedling  Bouteloua  hirsuta,  Andropogon  scoparius, 
furcatus,  and  nutans,  and  Sporoholus  asper  had  reached  heights  of  6  to  10 
inches  in  the  grassland  at  Lincoln,  the  bulk  of  the  root  systems  was  found  to 
occur  at  no  greater  depths  than  8  to  18  inches.  In  cultivated  areas  seedlings  of 
Bouteloua,  Sporoholus,  and  Liatris,  for  example,  reached  heights  of  3  or  4 
inches  in  44  days  and  the  roots  reached  depths  of  7  to  11  inches.  By  mid¬ 
summer  they  were  8  to  18  inches  tall,  and  the  root  depth  20  to  33  inches. 
The  excellent  growth  made  by  all  the  species  when  properly  spaced  in  fertile, 
cultivated  soil  with  adequate  holard  emphasizes  the  keen  competition  pre¬ 
vailing  in  stabilized  grassland.  In  the  natural  cover,  as  well  as  in  the  trench 
and  denuded  quadrat,  most  of  the  grasses  require  2  or  more  years  to  produce 
seed,  but  under  the  former  environment  73  per  cent  bore  seed  the  first  season. 
Because  of  the  lack  of  root  competition  encountered  by  plants  in  the  prairie, 


RESULTS  FOR  1920  AND  1921. 


141 


the  species  in  cultivated  soil  not  only  suffered  less  from  drought,  but  also  made 
a  greater  growth  and  tillered  more  heavily.  For  example,  Andropogon  nutans 
was  7  to  10  inches  tall  at  the  end  of  the  first  season  in  the  true-prairie  quadrats 
and  12  to  17  inches  in  the  adjacent  cultivated  field.  The  tap-root  of  Gleditsia 
reached  a  depth  of  40  inches  by  midsummer  and  that  of  Onagra  44  inches  at 
the  end  of  the  first  season,  while  Andropogon  scoparius  had  a  maximum  lateral 
spread  of  nearly  1.5  feet,  was  rooted  abundantly  to  26  inches  depth,  and  had  a 
maximum  penetration  of  4  feet.  These  are  typical  examples  of  many  findings. 
In  the  deep,  mellow  loess  soil  at  Peru,  Nebraska,  the  root  penetration  of 
seedlings  was  even  greater.  Of  the  40  blocks  of  sod  (9  species)  transplanted  at 
Burlington  no  species  died,  but  only  53  per  cent  (unwatered  sods)  had  flower- 
stalks,  as  compared  with  70  per  cent  at  Lincoln,  where  none  of  the  13  trans¬ 
planted  species  died  (23  blocks). 

In  the  edaphic  series,  the  low  prairie  exhibited  a  chresard  5  to  10  per  cent 
greater  than  that  of  high  prairie,  and  it  also  exceeded  that  at  Nebraska  City, 
where  unusually  dry  weather  prevailed.  However,  the  humidity  was  higher 
at  Nebraska  City  and  the  evaporation  correspondingly  less  than  on  low  prairie, 
which  was  more  mesophytic  than  high  prairie.  The  holard  on  the  gravel- 
knoll  and  at  Burlington  was  not  very  different,  frequently  falling  to  the 
hygroscopic  coefficient,  the  short-grasses  on  both  areas  drying  and  turning 
brown  late  in  July  or  in  August.  The  average  germination  was  highest  at 
Nebraska  City  (93  per  cent),  intermediate  on  low  prairie  (77;  86  per  cent 
on  high  prairie),  and  least  on  the  gravel-knoll  (71  per  cent).  The  average 
of  establishment  was  greatest  in  the  cultivated  area  at  Lincoln  (100  per 
cent),  75  per  cent  on  low  prairie,  70  per  cent  at  Nebraska  City,  and  only  15 
per  cent  on  the  gravel-knoll.  Thus,  all  stations  except  the  last  exceeded  high 
prairie  (42),  while  Burlington  with  25  per  cent  exceeded  the  gravel-knoll. 

As  to  sod  transplants  on  the  gravel-knoll,  all  showed  repeated  rolling  and 
drying  back  of  the  leaves;  only  a  few  flowered,  and  these  did  so  earlier  than 
elsewhere.  On  low  prairie  all  grew  well  and  blossomed.  The  transplants 
suffered  from  drought  in  the  salt-flats,  exhibiting  wilting  and  yellowing  of  the 
leaves  and  dwarfed  stature.  Seven  species,  mostly  from  upland,  succumbed  to 
insufficient  aeration  in  the  swamp,  and  four  in  the  Poa  zone.  All  survived  at 
Colorado  Springs,  where  they  were  transplanted  late,  but  none  made  a  good 
growth.  In  the  case  of  Spartina  cynosuroides  transplanted  from  swamp  to 
high  prairie  two  years  earlier,  many  leaves  reached  a  height  of  40  inches  and 
the  roots  were  abundant  to  9  or  10  feet  depth,  being  much  more  branched  than 
in  lowland.  Panicum  virgatum  showed  a  similar  growth. 

PHYSICAL  FACTORS  FOR  1921. 

The  season  of  1921  was  very  favorable  for  growth,  no  marked  drought 
periods  occurring  at  Lincoln,  where  at  least  5  and  usually  8  or  10  per  cent  of 
chresard  existed  at  all  times  and  at  all  depths  to  4  feet.  At  Phillipsburg  the 
echard  was  approached  once  in  July  and  twice  in  August,  no  water  being 
available  to  a  depth  of  4  feet  in  late  summer.  As  usual  conditions  were  much 
worse  at  Burlington.  At  no  time  was  water  available  in  the  third  or  fourth 
foot  of  soil,  while  after  June  30  it  was  depleted  repeatedly  above  the  hard-pan 
at  a  depth  of*  2  feet.  The  humidity  was  highest  at  Lincoln  and  lowest  at 
Burlington,  where  it  often  dropped  to  10  or  20  per  cent  in  the  late  afternoon. 


142  RESUME. 

Evaporation  increased  inversely  with  humidity  and  soil  moisture,  ranging 
from  8  to  27  c.  c.  daily  at  Lincoln,  8  to  43  c.  c.  at  Phillipsburg,  and  18  to  62 
c.  c.  at  Burlington.  The  remaining  conditions  for  plant  growth  were  also  most 
favorable  at  Lincoln,  intermediate  at  Phillipsburg,  and  poorest  at  Burlington. 

ECESIS  DURING  1921. 

The  germination  results  agreed  with  those  of  preceding  years,  Lincoln  being 
highest  (81  per  cent),  Phillipsburg  second  (68  per  cent),  and  Burlington  last 
(43  per  cent).  However,  owing  to  the  unusually  favorable  rainfall  following 
germination  at  Phillipsburg,  establishment  was  highest  here  (65  per  cent), 
intermediate  at  Lincoln  (40  per  cent),  and  least  at  Burlington  (7  per  cent). 
No  seedling  transplants  survived  at  Burlington,  but  54  per  cent  lived  at 
Lincoln,  and  75  per  cent  at  Phillipsburg.  Although  the  surface-sown  seeds 
germinated  better  than  those  in  the  trench,  establishment,  as  in  1920,  was 
least  on  the  surface,  next  in  the  trench,  and  best  in  denuded  quadrats,  the 
latter  exceeding  that  of  seedling  transplants.  As  to  the  1920  plantings,  the 
average  survival  during  1921  was  greatest  at  Lincoln  and  least  at  Burlington. 
An  examination  of  the  grasses  and  forbs  during  the  second  year  in  the  quadrats 
at  Phillipsburg  showed  that  they  were  well  established,  the  roots  penetrating 
to  depths  of  2.5  to  4  feet. 

Sods  on  the  high  prairie  all  did  well,  but  4  species  died  at  Burlington,  and 
the  rest,  including  those  that  had  been  repeatedly  watered,  were  represented 
by  mere  remnants  of  the  original  fine  blocks.  Of  those  transplanted  to  high 
prairie  in  1920,  all  survived  and  some  increased  their  area,  but  at  Burlington  1 
died,  while  all  suffered  from  drought  and  were  considerably  dwarfed.  By  mid¬ 
summer  of  the  second  season's  growth  in  the  short-grass  plains,  the  roots  were 
confined  to  the  surface  2  to  2.5  feet,  except  in  the  watered  area,  where  they 
penetrated  5  to  7  feet. 

As  to  the  other  stations,  the  season  at  Nebraska  City  was  one  of  drought, 
though  the  soil  usually  had  a  10  per  cent  chresard  at  all  depths  to  4  feet. 
This  exceeded  the  water-content  on  low  prairie,  where  the  chresard  in  the 
surface  6  inches  was  nearly  exhausted  in  June.  Conditions  on  the  gravel-knoll 
were  more  favorable  than  during  1920.  Evaporation  at  Nebraska  City  and 
low  prairie  was  lower  than  on  the  high  prairie  and  was  highest  on  the  gravel- 
knoll.  The  average  germination  at  the  three  stations  was  very  similar  (63 
to  76  per  cent)  and  in  all  cases  less  than  on  high  prairie  (81  per  cent).  The 
rate  of  establishment  was  in  the  following  order:  Nebraska  City  41  per  cent, 
high  prairie  40  per  cent,  low  prairie  38  per  cent,  and  gravel-knoll  29  per  cent, 
the  last  considerably  exceeding  Burlington  (7  per  cent) .  Seedling  transplants 
gave  the  best  growth  on  low  prairie  (92  per  cent),  next  at  Nebraska  City  (57 
per  cent),  then  high  prairie  (54  per  cent),  and  least  in  gravel-knoll  (14  per 
cent).  Four  species  of  sod  transplants  died  on  the  gravel-knoll,  and  three 
were  shaded  out  in  low  prairie,  while  all  survived  on  the  salt-flat  and  in  the 
swamp,  the  latter  being  much  drier  than  in  1920.  Of  the  1920  transplants, 
no  species  died  on  the  gravel-knoll,  one  succumbed  to  the  shade  in  low  prairie, 
one  died  on  the  salt-flat,  and  6  in  the  swamp  and  bluegrass  zone. 

PHYSICAL  FACTORS  FOR  1922. 

The  season  of  1922  was  fairly  favorable  for  growth,  except  for  the  latter 
part,  when  severe  drought  occurred  at  all  the  stations,  though  it  was  relatively 


RESULTS  FOR  1922. 


143 


less  marked  on  the  Great  Plains.  A  margin  of  at  least  5  per  cent  and  more, 
usually  7  to  11  per  cent,  chresard  existed  at  all  times  to  a  depth  of  4  feet  in  the 
high  prairie  at  Lincoln,  while  at  the  mixed-prairie  station  drought  began  late 
in  June  and  continued  throughout  the  season.  There  was  often  no  chresard 
to  a  depth  of  4  feet.  The  soil  in  spring  and  early  summer  was  as  usual  quite 
moist  at  Burlington,  but  deficiencies  were  marked  and  practically  continuous 
after  the  middle  of  June.  As  usual,  the  factors  were  most  favorable  in  true 
prairie  and  least  so  on  the  Great  Plains. 

ECESIS  DURING  1922. 

As  for  the  two  years  preceding,  the  average  germination  under  all  methods 
of  planting  was  highest  at  Lincoln  (74  per  cent),  intermediate  at  Phillipsburg 
(63  per  cent),  and  least  at  Burlington  (44  per  cent).  In  surface  sowing  Phil¬ 
lipsburg  slightly  outranked  Lincoln,  due  to  differences  in  soil  structure.  This 
also  accounts  for  the  greater  survival  of  seedling  transplants  at  the  former, 
the  percentages  being  78,  70,  and  26  respectively.  Establishment  was 
decidedly  highest  in  true  prairie,  viz,  62  per  cent;  it  was  but  39  per  cent  in 
mixed  prairie,  and  26  per  cent  in  the  short-grass  plains.  Germination  aver¬ 
aged  best  on  the  surface,  next  in  denuded  quadrats,  and  least  in  the  trench, 
but  establishment  was  in  the  following  order :  denuded  quadrats,  trench,  and 
surface,  the  last  giving  the  lowest  percentage.  Bouteloua  gracilis  made  the 
best  growth  in  the  quadrats  at  Burlington  and  the  least  at  Lincoln,  but  for  all 
of  the  other  species  the  growth-rate  was  in  the  sequence  of  increasing  water- 
content,  i.  e.,  eastward.  Andropogon  nutans,  Kuhnia  glutinosa,  Bouteloua 
racemosa ,  and  Panicum  virgatum  were  4  to  12  inches  tall  at  Lincoln,  3  to  9 
inches  at  Phillipsburg,  and  1  to  5  inches  at  Burlington. 

The  survival  for  the  1920  surface-sowings  was  33  per  cent  at  Burlington 
only;  for  the  trench  it  was  33  per  cent  at  Lincoln  and  Phillipsburg,  and 
for  the  quadrats  55  per  cent  at  Lincoln  and  43  per  cent  at  Burlington,  the 
plants  at  Phillipsburg  having  been  mostly  excavated  for  root  study.  The 
average  survival  of  1921  plantings  and  seedling  transplants  was  greatest  at 
Phillipsburg  and  lowest  at  Burlington.  Two  species  died  out  of  the  26  trans¬ 
planted  to  high  prairie  in  1922;  these  were  both  dicotyls  with  strong  tap¬ 
roots.  All  of  the  13  species  of  grasses  transplanted  to  Burlington  survived, 
although  they  flowered  less  than  at  Lincoln  and  nearly  all  were  dwarfed.  Of 
the  1920  sod  transplants,  2  died  on  high  prairie  during  1922,  but  only  1  at 
Burlington,  although  many  more  individuals  out  of  the  40  transplanted 
blocks  of  sod  succumbed  here.  None  of  the  1921  transplants  died  on  the 
high  prairie;  several  increased  their  territory,  and  12  of  the  16  species  blos¬ 
somed.  At  Burlington  several  individuals  died,  but  only  1  species  vanished 
entirely.  Agropyrum  spicatum  and  Bouteloua  racemosa  were  the  sole  survivors 
of  the  unwatered  lot. 

As  to  the  other  stations,  the  season  at  Nebraska  City  was  one  marked  by 
drought  in  June  and  August.  However,  the  soil  usually  had  a  chresard  of  8 
per  cent  below  the  first  foot,  but  that  in  the  surface  foot,  which  most  critically 
affects  seedlings,  was  practically  exhausted  two  or  three  times  during  the 
summer,  being  less  favorable  than  in  1921.  Conditions  as  to  the  holard  were 
more  favorable  on  low  prairie,  where  a  considerable  excess  prevailed  over  that 
on  high  prairie.  On  the  gravel-knoll  the  grama  grasses  dried  during  the 


144  RESUME. 

drought,  as  no  moisture  was  available  in  the  first  2  feet  of  soil.  The  germina¬ 
tion  of  surface-sown  seed  was  not  greatly  different  at  the  three  stations 
(70  to  84  per  cent),  this  method  of  sowing  giving  the  best  germination.  The 
average  germination  was  67  per  cent  at  Nebraska  City,  75  on  low  and  74  on 
high  prairie.  Establishment  gave  the  usual  sequence  with  respect  to  method 
of  planting.  It  averaged  46  per  cent  at  Nebraska  City,  62  per  cent  on  high 
prairie,  and  only  50  per  cent  on  the  more  densely  shaded  low  prairie,  where 
light  values  ranged  from  2  to  10  per  cent.  Seedlings  did  best  on  high  prairie 
(70  per  cent)  where  they  were  watered,  next  at  Nebraska  City  (59  per  cent), 
and  poorest  on  low  prairie  (45  per  cent).  Three  of  the  sod  transplants  on  low 
prairie  succumbed  to  the  dense  shade,  as  did  4  in  the  swamp,  while  one  died  on 
the  salt-flat.  Of  the  1920  sods,  3  died  on  the  gravel-knoll,  4  were  shaded  out 
in  low  prairie,  and  1  died  in  the  salt-flat,  but  no  further  mortality  occurred  in 
the  rapidly  drying  swamp.  Of  the  1921  transplants,  3  more  died  on  the 
gravel-knoll,  5  in  low  prairie,  1  in  the  salt-flat,  and  2  in  the  swamp. 

BEHAVIOR  DURING  1923. 

In  1923,  a  season  with  high  spring  and  summer  rainfall  at  the  western 
stations,  the  plants  made  an  excellent  growth.  Not  only  was  the  rainfall  above 
the  normal,  but  the  rains  were  also  well  distributed,  drought  periods  being 
fewer  and  shorter  than  usual.  At  Lincoln  the  precipitation  for  spring  and 
summer  averaged  below  normal.  The  preceding  fall  and  winter  had  been  one 
of  unusually  severe  drought,  and  high  losses  were  sustained  at  all  the  stations. 
In  the  major  climatic  stations  these  were  greatest  at  Burlington,  intermediate 
at  Phillipsburg,  and  least  at  Lincoln.  For  example,  losses  of  the  1921  plant¬ 
ings  and  transplants  were  43,  28,  and  13  per  cent  in  the  above  sequence  of 
stations.  The  mortality  at  all  stations  averaged  greatest  for  the  plants  of  a 
single  year’s  establishment,  next  for  those  2  years  old,  and  least  for  those 
established  for  3  seasons,  e.  g.,  the  respective  losses  at  Burlington  being  85, 
43,  and  16  per  cent.  The  survival  was  greatest  in  denuded  quadrats,  this 
method  even  outranking  that  of  transplanting  blocks  of  sod. 

In  the  survival  of  surface-sown  plants  for  all  years  Phillipsburg  ranked  first 
(14  per  cent),  Burlington  second  (11  per  cent),  and  Lincoln  last  (9  per  cent). 
The  average  germination  was  respectively  79,  45,  and  76  per  cent,  Lincoln 
taking  second  and  Burlington  third  place.  The  average  germination  in 
trenches  decreased  from  Lincoln  westward,  the  percentages  being  85,  59,  and 
21  respectively.  The  average  survival  for  all  years  at  the  end  of  1923  was  in 
the  same  order,  the  percentages  being  27,  21,  and  0  respectively.  Germination 
in  denuded  quadrats  was  greatest  at  Lincoln  for  every  year  except  one,  and 
least  at  Burlington,  with  one  exception,  the  percentages  for  the  three  stations 
being  81,  73,  and  60.  With  a  single  exception,  establishment  was  likewise  in 
the  same  order,  viz,  72  per  cent  in  true  prairie,  60  per  cent  in  mixed  prairie, 
and  43  per  cent  in  the  short-grass  plains,  and  this  was  also  true  of  survival  at 
the  end  of  1923,  the  percentages  being  44,  22,  and  21  respectively.  Hence, 
while  surface-sowing  ranked  highest  in  germination,  it  resulted  in  the  lowest 
estabishment. 

Transplanted  seedlings  usually  did  best  at  Phillipsburg,  the  average  survival 
at  the  end  of  1923  being  44  per  cent  as  compared  with  37  per  cent  at  Lincoln 
and  3  per  cent  at  Burlington. 


RESULTS  FOR  1923. 


145 


Permanent  establishment  by  the  end  of  1923  under  the  three  methods  of 
planting  was  44,  27,  and  9  per  cent  respectively  at  Lincoln,  22,  21,  and  14  per 
cent  at  Phillipsburg,  and  21,0,  and  1 1  per  cent  at  Burlington.  This  was  always 
greatest  in  the  denuded  quadrats  and  next  greatest  in  the  trench. 

The  results  of  seeding  and  transplanting  at  Nebraska  City  and  on  low  prairie 
are  not  greatly  different,  although  often  somewhat  better  than  on  high 
prairie,  while  ecesis  on  the  gravel-knoll  was  often  only  slightly  higher  than  that 
at  Burlington.  At  the  latter,  as  on  the  gravel-knoll,  drought  was  the  deciding 
factor,  while  on  low  prairie,  as  well  as  at  Nebraska  City,  light  played  the 
dominant  role. 

Certain  species  were  found  to  survive  more  frequently  than  others.  Out 
of  the  total  plantings  at  Nebraska  City,  Lincoln,  Phillipsburg,  and  Burlington, 
beginning  with  1920,  Andropogon  nutans  survived  in  35  different  places  by 
the  end  of  1923.  The  survival  of  other  species  was  in  the  following  order,  the 
figures  indicating  the  different  number  of  places  in  which  they  survived  : 
Bouteloua  gracilis  18,  B.  racemosa  15,  B.  hirsuta  14,  Sporobolus  asper  11, 
Aristida  purpurea,  Elymus  canadensis,  and  Liatris  punctata  10  each,  Andro- 
pogon  scoparius  8,  A.  furcaius  7,  Petalostemon  candidus  6,  Stipa  spartea, 
Desmodium  canescens,  and  Liatris  scariosa  5  each,  Kuhnia  glutinosa  4,  Panicum 
virgatum,  Stipa  viridula,  Symphoricarpus  occidentalis  3  each,  Gleditsia 
triacanthus,  Symphoricarpus  vulgaris,  Koeleria  cristata,  Ratibida  columnaris, 
Robinia  pseudacacia,  and  Acer  saccharinum  2  each,  and  Stipa  comata, 
Agropyrum  glaucum,  Pinus  ponderosa,  and  Acer  negundo  each  only  1. 

As  regards  sod  transplants,  by  the  fall  of  1923  over  half  of  the  1920  plantings 
at  Burlington  had  died.  Agropyrym  glaucum  alone  remained  in  the  un¬ 
watered  area.  The  1921  transplants,  half  of  which  were  watered,  lost  15  out 
of  22  individuals,  Agropyrum  and  Bouteloua  racemosa  alone  surviving  in  the 
unwatered  area,  while  practically  all  of  the  rest  showed  clearly  that  they 
would  not  last  much  longer.  83  per  cent  of  the  1922  transplants  were  winter- 
killed,  and  at  the  end  of  the  second  season  Bouteloua  gracilis  and  remnants  of 
2  other  species  alone  remained.  These  results  clearly  reveal  the  uncongenial 
nature  of  the  Great  Plains,  in  so  far  as  prairie  species  are  concerned. 

Relatively  few  species  died  on  the  high  prairie,  even  Spartina  cynosuroides 
and  Panicum  virgatum  forming  seed.  Of  the  1920  plantings  only  6  individuals 
had  died,  including  2  plants  of  Distichlis  spicata,  which  never  flourished  out 
of  its  owtl  saline  habitat.  Of  the  1921  plantings  a  single  one  succumbed.  Six 
forbs  among  the  1922  plantings  died,  and  1  lot  of  Bouteloua  gracilis.  Several 
of  the  species  had  considerably  extended  their  area. 

On  the  gravel-knoll  the  mortality  was  much  greater,  although  here  likewise 
several  low-prairie  species  became  permanently  established,  their  roots  ex¬ 
tending  well  into  the  clay  subsoil  below  4  feet.  Three  species  of  the  1920  and 
7  of  the  1921  lot  succumbed,  but  others  planted  in  1919  still  survived,  Bulbilis 
and  Agropyrum  being  quite  at  home.  Nearly  all  were  somewhat  dwarfed,  and 
they  began  growth  and  matured  earlier  than  at  the  other  Lincoln  stations. 

Exceedingly  interesting  results  were  obtained  on  low  prairie.  Of  the  14 
species  and  28  blocks  of  sods  transplanted  in  1920,  all  flourished,  including 
Bulbilis  and  Bouteloua  gracilis.  By  the  second  season,  however,  1  species  was 
shaded  out,  4  the  next,  and  1  in  1923,  so  that  by  the  end  of  the  fourth  summer 
the  dominants  of  the  low  prairie  alone,  viz,  Andropogon  nutans  and  furcatus, 


146  RESUME. 

Panicum  virgatum,  Elymus  canadensis ,  and  Spartina  cynosuroides  were 
flourishing,  Stipa,  a  single  Koeleria,  and  Andropogon  scoparius  surviving  from 
the  high  prairie.  Of  the  1921  transplants,  5  subclimax  dominants  developed 
normally,  but  of  the  10  species  remaining  all  had  succumbed  but  3  represented 
by  mere  remnants.  Two  or  three  years  were  sufficient  for  the  tail-grasses  to 
overshade  and  cause  Bulbilis  and  Bouteloua  gracilis  and  hirsuta  to  disappear. 
This  applies  also  to  several  true-prairie  dominants.  Of  the  1922  transplants  a 
total  of  11  species  had  succumbed  by  the  end  of  1923,  the  process  of  elimina¬ 
tion  being  well  under  way. 

On  the  salt-flats,  while  the  plants  were  able  in  most  cases  to  tolerate  condi¬ 
tions  (only  6  species  among  the  three  years’  plantings  succumbing),  they 
made  a  very  poor  growth,  did  not  extend  their  territory,  and  seeded  very 
poorly.  For  the  most  part  they  had  a  paler  color  and  in  every  way  reflected 
the  unfavorable  environment,  except  the  indigenous  Distichlis  alone. 

Transplants  in  the  swamp  lost  heavily,  at  first- from  poor  aeration  and  later 
from  lack  of  light,  after  a  dam  was  built  above  the  experimental  area  and  the 
swamp  dried  out.  High-prairie  species  were  most  affected  and  died  in  greatest 
numbers,  the  flower-stalk  often  rotting  off  at  the  surface  of  the  saturated  soil. 
By  1923,  Spartina,  Panicum  virgatum,  and  Elymus  canadensis,  all  of  which 
grew  well,  were  the  only  survivors  among  the  13  species  planted  in  the  swamp, 
while  these  and  Poa  pratensis  were  the  4  survivors  of  a  similar  lot  in  the  Poa 
zone,  which  was  now  overgrown  with  Spartina. 

During  the  course  of  the  experiment  it  was  found  that  species  of  widely 
different  families  exhibit  the  phenomenon  of  dormancy,  the  seeds  lying 
in  the  soil  for  one  or  more  years  before  germinating.  Among  the  most  con¬ 
spicuous  cases  the  following  may  be  enumerated:  Robinia  pseudacacia,  Gledit- 
sia  triacanthus,  Petalostemon  candidus,  and  Lespedeza  capitata  among  legumes ; 
Sporobolus  asper,  Andropogon  nutans,  Panicum  virgatum,  and  Andropogon 
furcatus  among  grasses;  and  likewise  Kuhnia  glutinosa,  Corylus  americana,  and 
Acer  negundo.  While  the  volunteer  growth  of  these  plants  during  the  second 
or  third  year  has  not  been  recorded  in  detail,  because  of  the  risk  of  confusion, 
it  may  be  stated  that  in  general  they  suffered  the  same  fate  as  the  original 
plantings. 

BEHAVIOR  OF  TREES  AND  SHRUBS. 

The  fate  of  trees  and  shrubs  planted  or  transplanted  by  rhizomes  into  grass¬ 
land  is  of  especial  interest.  The  trees  employed  were  Acer  negundo,  A. 
saccharinum,  Gleditsia  triacanthus,  Robinia  pseudacacia,  and  Pinus  ponderosa, 
together  with  the  following  shrubs:  Corylus  americana,  Symphoricarpus  occi- 
dentalis,  and  S.  vulgaris.  At  Burlington  none  survived  longer  than  the  first 
season,  and  at  Phillipsburg  the  only  survivors  at  the  end  of  1923  were  the  2 
species  of  Symphoricarpus  planted  in  1921.  Corylus  (delayed  growth), 
Robinia,  Gleditsia,  and  Acer  saccharinum  of  the  1922  planting,  and  Robinia 
of  1921  survived  on  high  prairie.  On  low  prairie  Symphoricarpus  occidentalis 
of  the  1921  planting  and  Acer  saccharinum  of  1922  alone  survived.  None  lived 
on  the  gravel-knoll,  but  at  Nebraska  City  both  species  of  Symphoricarpus  of 
1921  and  Acer  negundo  and  Pinus  ponderosa  of  1922  were  alive  at  the  end  of  the 
summer  of  1923.  However,  as  shown  by  a  series  of  earlier  experiments  with 
trees  at  Lincoln,  the  results  of  which  are  as  yet  unpublished,  the  possibility  of 


CLIMATIC  STATIONS. 


147 


tree-growth  in  stabilized  grassland  is  almost  nil,  since  tree  seedlings  are 
killed  by  drought  on  upland  and  are  shaded  out  on  lowland. 

GERMINATION  AND  SURVIVAL  AT  THE  CLIMATIC  STATIONS. 

The  percentage  of  germination  for  each  year  and  for  each  method  and  the 
percentage  of  survival  for  the  first  year  of  planting  as  well  as  succeeding  years 
are  given  in  table  55.  The  percentage  of  germination  under  surface  sowing 
was  greatest  at  Lincoln  during  1920,  and  at  Phillipsburg  during  1921  and 
1922,  while  it  was  least  at  Burlington  for  all  three  years.  The  averages  for  the 
three  years  are  Phillipsburg  79  per  cent,  Lincoln  76  per  cent,  and  Burlington 
45  per  cent  (table  56).  In  regard  to  establishment,  Burlington  ranked  first  in 
1920  (clearly  an  erratic  case),  Phillipsburg  in  1921,  and  Lincoln  in  1922.  As 
to  the  survival  of  plants  of  all  years,  at  the  end  of  1923  Phillipsburg  was  first 
with  14  per  cent,  Burlington  second,  11  per  cent,  and  Lincoln  third,  9  per  cent. 
The  greater  germination  and  establishment  at  Phillipsburg  were  probably  due 
to  the  structure  of  the  soil  (p.  12). 

Germination  in  the  trenches  was  highest  at  Phillipsburg  in  1920,  but  at 
Lincoln  for  the  other  years,  Burlington  coming  last.  The  average  germination 
for  the  three  seasons  was  greatest  at  Lincoln  (85  per  cent),  next  at  Phillips¬ 
burg  (59  per  cent),  and  lowest  at  Burlington  (21  per  cent).  Survival  in  1920 
and  for  1923  was  greatest  at  Lincoln,  but  in  1921  greatest  at  Phillipsburg, 
Burlington  regularly  ranking  third.  However,  in  the  survival  for  all  plantings 
at  the  end  of  1923,  the  sequence  is  Lincoln,  Phillipsburg,  and  Burlington,  with 
respective  percentages  of  27,  21,  and  0. 

Germination  in  the  denuded  quadrats  was  greatest  at  Lincoln  during  1920 
and  1922,  and  least  at  Burlington,  except  in  1921,  when  it  exceeded  Phillips¬ 
burg  and  Lincoln.  The  average  germination  for  the  three  years  at  the  several 
stations  was  81,  73,  and  60  per  cent,  in  the  order  of  decreasing  rainfall. 
Establishment  was  also  greatest  at  Lincoln  every  year  and  least  at  Burlington, 
except  during  1922,  when  the  latter  exceeded  that  at  Phillipsburg.  The 
average  establishment  for  the  three  years  was  72  per  cent  in  the  true  prairie, 
60  per  cent  in  mixed  prairie,  and  43  per  cent  in  the  short-grass  plains.  The 
percentage  of  survival  for  all  plantings  in  quadrats  for  the  three  years  was,  in 
the  above  order,  44,  22,  and  21. 

Transplanted  seedlings  did  best  at  Phillipsburg  both  during  1921  and  1922 
and  poorest  at  Burlington.  Moreover,  the  average  survival  at  the  end  of  1923 
was  greatest  at  Phillipsburg  (44  per  cent),  next  at  Lincoln  (36  per  cent),  and 
least  at  Burlington  (3  per  cent).  The  explanation  of  the  better  survival  in  the 
mixed  prairie  seems  clearly  to  be  sought  in  the  more  favorable  soil  structure. 

With  reference  to  the  success  of  the  various  methods,  surface  sowing  gave 
the  poorest  results  as  to  germination  in  1920,  but  the  best  the  other  two 
seasons,  the  quadrat  ranking  second  (first  in  1920),  and  the  trench  third.  On 
the  other  hand,  establishment  was  always  greatest  in  the  denuded  quadrat, 
second  in  the  trench,  and  least  on  the  surface.  The  survival  for  all  years  at  the 
end  of  1923  was  greatest  in  denuded  quadrats,  and  least  on  the  surface. 
At  Lincoln  under  the  three  methods  it  was  44,  27,  and  9  per  cent,  re¬ 
spectively,  at  Phillipsburg  22,  21,  and  14  per  cent,  and  at  Burlington  21,  0, 
and  11  per  cent.  The  seedling-transplant  method  was  somewhat  less  suc¬ 
cessful  than  sowing  in  quadrats,  but  more  satisfactory  than  sowing  in  trenches. 


148 


RESUME. 


The  persistence  of  plants  is  high  after  surviving  a  single  growing-season,  but 
the  mortality  is  also  usually  greater  during  the  second  winter  and  summer 
than  for  any  year  afterward. 

During  the  three  years  the  average  germination  for  all  methods  was  greatest 
in  true  prairie  (81  per  cent),  second  in  mixed  prairie  (70  per  cent),  and  least 
at  Burlington  (42  per  cent).  The  average  establishment  was,  in  the  same 
sequence  of  stations,  48,  46,  and  20  per  cent,  as  was  also  the  average  survival 
at  the  end  of  1923,  viz,  27,  19,  and  11  per  cent.  Thus,  the  experimental 
evidence  clearly  indicates  that  the  best  conditions  for  growth  are  to  be  found 
in  true  prairie  and  the  least  favorable  ones  in  the  short-grass  plains,  conditions 
in  the  mixed  prairie  being  intermediate. 

GERMINATION  AND  SURVIVAL  AT  THE  EDAPHIC  STATIONS. 

Results  from  the  series  of  edaphic  stations  show  that  the  germination  of 
surface-sown  seeds  was  very  similar  in  the  low  prairie  and  at  Nebraska  City 
during  the  three  years,  where  it  slightly  exceeded  that  on  the  high  prairie  at 
Lincoln.  The  survival  at  the  end  of  the  first  season  averaged  greater  at  both 


Table  55. — Per  cent  of  germination  and  survival  at  all  stations,  1920-1923. 


Surface  sowing. 

Trench  sowing. 

Station. 

P.  ct. 
ger¬ 
mina¬ 
tion. 

P.  ct.  survival. 

P.  ct. 

ger¬ 

mina¬ 

tion. 

P.  ct.  survival. 

1920. 

1921. 

1922. 

1923. 

1920. 

1921. 

1922. 

1923. 

1920. 

Lincoln  (high  prai¬ 
rie)  . 

66 

0 

92 

45 

42 

33 

33 

Phillipsburg . 

50 

0 

.  . 

.  , 

.  , 

100 

33 

33 

33 

33 

Burlington . 

46 

33 

33 

33 

33 

15 

0 

.  . 

.  . 

.  . 

1921. 

Lincoln  (high  prai¬ 
rie)  . 

79 

9 

(9) 

(9) 

92 

45 

36 

36 

Phillipsburg . 

100 

•  . 

83 

50 

25 

43 

.  , 

50 

33 

17 

Burlington . 

38 

•  . 

0 

•  • 

•  • 

15 

•  • 

0 

•  . 

•  • 

1922. 

Lincoln  (high  prai¬ 
rie)  . 

82 

50 

17 

70 

63 

13 

Phillipsburg . 

86 

•  . 

•  • 

42 

16 

35 

.  . 

•  . 

25 

13 

Burlington . 

50 

•  • 

.  . 

0 

•  • 

32 

.  , 

.  . 

14 

0 

1920. 

Gravel-knoll  (Lin¬ 
coln)  . 

71 

30 

0 

Low  prairie  (Lin¬ 
coln)  . 

75 

33 

(17) 

(17) 

(17) 

57 

100 

50 

50 

50 

Nebraska  City.  . . . 

80 

50 

38 

(38) 

(38) 

100 

60 

30 

20 

20 

1921. 

Gravel-knoll  (Lin¬ 
coln) . 

55 

17 

0 

Low  prairie  (Lin¬ 
coln)  . 

78 

14 

0 

0 

75 

17 

Excavated 
for  roots. 

Nebraska  City.  . . . 

78 

29 

29 

29 

50 

,  , 

33 

17 

17 

1922. 

Low  prairie  (Lin¬ 
coln) . 

84 

25 

6 

60 

64 

43 

Nebraska  City.  . . . 

70 

•  • 

50 

21 

62 

33 

15 

EDAPHIC  STATIONS. 


149 


Table  55. — Per  cent  of  germination  and  survival  at  all  stations,  1920-1923 — Continued, 


Denuded  quadrats,  sowing. 

Seedling  trans- 

Station. 

P.  ct. 
ger¬ 
mina¬ 
tion. 

P.  ct.  survival. 

plants,  p.  ct. 
survival. 

1920. 

1921. 

1922. 

1923. 

1921. 

1922. 

1923. 

1920. 

Lincoln  (high  prairie) . 

100 

80 

55 

55 

55 

Phillipsburg . 

90 

67 

67 

Exca 

vated 

Burlington . 

54 

43 

43 

for  r 
43 

oots. 

43 

1921. 

Lincoln  (high  prairie) . 

71 

65 

30 

30 

54 

39 

23 

Phillipsburg . 

61 

63 

31 

31 

75 

58 

50 

Burlington . 

76 

21 

11 

5 

0 

1922. 

Lincoln  (high  prairie) . 

71 

72 

48 

70 

50 

Phillipsburg . 

69 

50 

36 

78 

37 

Burlington . 

50 

64 

14 

26 

5 

1920. 

Gravel-knoll  (Lincoln) . 

71 

0 

Low  prairie  (Lincoln) . 

100 

91 

82 

73 

45 

Nebraska  City . 

100 

100 

90 

80 

70 

1921. 

Gravel-knoll  (Lincoln) . 

71 

40 

30 

20 

14 

14 

14 

Low  prairie  (Lincoln) . 

75 

83 

42 

25 

92 

69 

31 

Nebraska  City . 

68 

60 

40 

40 

57 

57 

50 

1922. 

Low  prairie  (Lincoln) . 

81 

60 

50 

45 

39 

Nebraska  City . 

69 

54 

36 

59 

45 

¥ 

Note:  Numbers  in  parenthesis  indicate  that  the  plants  had  merged  into  the  native  sod  and 
were  not  traced  further. 


stations  (low  prairie  24,  Nebraska  City  43  per  cent)  than  on  high  prairie  (20 
per  cent),  while  the  average  survival  at  the  close  of  1923  was  respectively  8, 
29,  and  9  per  cent. 

The  average  germination  in  the  trenches  for  all  years  was  least  on  the  gravel- 
knoll,  63  per  cent;  it  reached  64  per  cent  in  low  prairie  and  71  per  cent  at 
Nebraska  City,  as  compared  with  85  per  cent  on  high  prairie.  However, 
ecesis  on  the  gravel-knoll  was  less  than  half  that  on  high  prairie  (23  in  contrast 
to  51  per  cent),  while  in  low  prairie  and  at  Nebraska  City  it  was  60  and  42  per 
cent  respectively.  The  survival  at  the  end  of  1923  was  nil  on  the  gravel- 
knoll,  31  per  cent  in  low  prairie,  and  17  per  cent  at  Nebraska  City,  as  com¬ 
pared  with  27  per  cent  on  high  prairie. 

Germination  in  denuded  quadrats  averaged  71,  85,  and  79  per  cent  on  gravel 
knoll,  low  prairie  and  Nebraska  City  respectively,  in  contrast  to  81  per  cent  on 
high  prairie.  The  corresponding  percentages  were  20,  78,  and  71,  as  against 
72  on  high  prairie,  the  survival  at  the  end  of  1923  being  10,  40,  49,  and  44  per 
cent  respectively. 

The  ecesis  of  seedling  transplants  was  14  per  cent  on  the  gravel-knoll  (1921 
only),  68  per  cent  in  low  prairie,  and  58  per  cent  at  Nebraska  City,  as  compared 
with  62  per  cent  on  high  prairie.  The  respective  survival  at  the  end  of  1923 
was  14,  35,  and  48  per  cent,  as  against  36  per  cent  on  high  prairie.  Thus, 


150 


RESUME. 


Table  56. — Summary  of  percentages  of  germination  and  survival. 

Surface  Sowing. 


Station. 


Lincoln  (high  prairie). 


Phillipsburg. 


Burlington . 


Low  prairie  (Lincoln). 


Nebraska  City. 


Year  of 
plant¬ 
ing. 


1920 

1921 

1922 

1920 

1921 

1922 

1920 

1921 

1922 

1920 

1921 

1922 

1920 

1921 

1922 


P.  ct. 
germina¬ 
tion. 


66 

79 
82 
50 

100 

86 

46 

38 

50 

75 

78 

84 

80 
78 
70 


Aver¬ 

age. 


76 

79 

45 

79 

76 


Survival 
at  end  of 
first  year. 


0 

9 

50 

0 

83 

42 

33 

0 

0 

33 

14 

25 

50 

29 

50 


Aver¬ 

age. 


20 


42 


11 


24 


43 


Survival 
at  end  of 
1923. 


0 

9 

17 

0 

25 

16 

33 

0 

0 

17 

0 

6 

38 

29 

21 


Aver¬ 

age. 


9 


14 


11 


8 


29 


Trench  Sowing. 


Lincoln  (high  prairie) . 


Phillipsburg. 


Burlington . 

Gravel-knoll  (Lincoln) , 

Low  prairie  (Lincoln) . 

Nebraska  City . 


1920 

1921 

1922 

1920 

1921 

1922 

1920 

1921 

1922 

1920 

1921 

1920 

1921 

1922 

1920 

1921 

1922 


92 

92 

70 
100 

43 

35 

15 

15 

32 

71 
55 
57 
75 
60 

100 

50 

62 


85 

59 

21 

63 

64 

71 


33 


51 


36 


5 


23 

60 

42 


33 

36 

13 

33 

17 

13 

0 

0 

0 

0 

0 

50 

Excav. 

43 

20 

17 

15 


27 

21 

0 

0 

31 

17 


Denuded  Quadrats. 


Lincoln  (high  prairie). 


Phillipsburg . 


Burlington . 


Gravel-knoll  (Lincoln) . 
Low  prairie  (Lincoln) . 


Nebraska  City. 


1920 

1921 

1922 

1920 

1921 

1922 

1920 

1921 

1922 

1920 

1921 

1920 

1921 

1922 

1920 

1921 

1922 


100 

71 

71 

90 

61 

69 

54 

76 

50 

71 

71 

100 

75 

81 

100 

68 

69 


81 

73 

60 

71 

85 

79 


80 

65 

72 

67 

63 
50 
43 
21 

64 
0 

40 

91 

83 

60 

100 

60 

54 


72 

60 

43 

20 

78 

71 


55 

30 

s  48  < 

!  Excav. 

31 
36 
43 

5 
14 
0 

20 
45 
25 
50 
70 
40 
36 


44 

22 

21 

10 

40 

49 


TRANSPLANTS. 


151 


Table  56. — Summary  of  'percentages  of  germination  and  survival — Continued. 

Seedling  Transplants. 


Station. 


Lincoln  (high  prairie) 

Phillipsburg . 

Burlington . 

Gravel-knoll  (Lincoln) . .  . 
Low  prairie  (Lincoln) 

Nebraska  City . 


Year  of 
plant¬ 
ing. 


P.  ct. 
germina¬ 
tion. 


Aver¬ 

age. 


Survival 
at  end  of 
first  year. 


54 

70 

75 

78 

0 

26 

14 

92 

45 

57 

59 


Aver¬ 

age. 


62 

77 

13 

14 
68 

58 


Survival 
at  end  of 
1923. 


23 

50 

50 

37 

0 

5 

14 

31 

39 

50 

45 


Aver¬ 

age. 


36 

44 

3 

14 

35 

48 


no  consistent  differences  are  to  be  found  between  the  low-prairie  station 
at  Lincoln,  which  is  really  a  postclimax  stage  in  the  true-prairie  climate,  and 
the  subclimax  prairie  at  Nebraska  City,  both  averaging  somewhat  better  than 
the  high-prairie  station  at  Lincoln.  The  gravel-knoll  station,  climatically  a 
preclimax  to  the  true  prairie,  excelled  Burlington  in  percentage  of  germina¬ 
tion  and  establishment,  but  barely  equaled  it  in  survival  at  the  end  of  1923. 


SURVIVAL  OF  SOD  TRANSPLANTS. 

While  the  number  of  species  lost  at  Burlington  from  the  1920  transplanting 
was  the  same  as  that  at  Lincoln,  the  individual  losses  were  far  greater,  owing 
to  the  transplanting  of  a  larger  number  of  blocks  of  each  species  at  the  plains 
station.  The  relative  losses  for  1921  were  representative.  Losses  in  individ¬ 
uals  on  the  gravel-knoll  were  consistently  high,  while  those  on  low  prairie 
were  similarly  high,  though  the  cause  for  the  latter  was  not  drought,  but 
shade.  The  losses  in  the  swamp  were  greatest  during  1920,  because  of  poor 
aeration  due  to  an  excessive  amount  of  water,  while  later  losses  were  caused 
almost  entirely  by  the  density  of  shade.  While  in  general  the  high-prairie 
species  were  the  ones  to  disappear  from  swamp  and  low  prairie,  no  consistent 
loss  of  individual  species  occurred  at  the  other  stations.  Excluding  the  losses 
of  1923,  owing  to  the  very  dry  fall  and  winter,  the  following  species  suffered 
total  loss  in  as  many  instances  as  are  indicated  by  the  number:  Koeleria 
cristata  14;  Andropogon  scoparius  7;  Elymus  canadensis,  Poa  pratensis, 
Agropyrum  glaucum,  and  Bouteloua  racemosa  6  each;  Distichlis  spicata  5; 
Stipa  spartea  and  Andropogon  nutans  4  each;  Bouteloua  gracilis,  Panicum 
virgatum,  Andropogon  furcatus  3  each;  and  Bouteloua  hir^uta,  Bulbilis  dacty- 
loides  and  Sporobolus  asper  1  or  2  each. 

PHYTOMETRIC  METHODS. 

In  spite  of  the  abnormal  weather  during  1923,  the  investigation  of  the 
transpiration  of  standard  plants  and  sod-cores  of  native  and  cultivated  spe¬ 
cies,  and  of  the  growth  of  natural  cover  and  crops,  as  shown  by  cut-quadrats, 
yielded  results  of  value  in  confirmation  of  those  obtained  by  the  methods  of 
experimental  vegetation.  This  was  especially  true  of  the  cut-quadrats,  as 


152  RESUME. 

these  also  extended  through  a  series  of  nearly  normal  years.  They  not  only 
demonstrated  the  close  dependence  of  grassland  and  crop  communities  upon 
rainfall  and  water-content,  but  also  the  intimate  relationship  of  the  various 
prairie  climaxes  and  climates.  The  evidence  drawn  from  germination,  ecesis, 
function,  and  growth  was  corroborated  in  large  measure  by  the  adaptation 
shown  in  leaf-structure,  though  this  was  more  or  less  obscured  by  the  fixity  of 
type  in  certain  species. 


Table  57. — Summary  of  sod  transplants. 


Station. 

No.  of 

No.  of 

Loss  of 

species  (not  individuals). 

species. 

trans¬ 

plants. 

1920. 

1921. 

1922. 

1923. 

1920. 

Lincoln  (high  prairie) . 

13 

23 

0 

0 

2 

0 

Burlington . 

9 

40 

0 

1 

1 

0 

Gravel-knoll . 

11 

28 

0 

0 

3 

0 

Low  prairie . 

14 

28 

0 

1 

4 

1 

Salt-flat . 

13 

17 

0 

1 

1 

0 

Swamp . 

13 

13 

7 

2 

0 

1 

Poa  zone  in  swamp . 

13 

13 

4 

4 

0 

0 

1921. 

Lincoln  (high  prairie) . 

15 

16 

0 

0 

1 

Burlington . 

11 

22 

4 

1 

3 

Gravel-knoll . 

14 

18 

4 

3 

0 

Low  prairie . 

15 

16 

3 

5 

1 

Salt-flat . 

15 

18 

0 

1 

1 

Swamp . 

14 

14 

0 

2 

7 

Poa  zone  in  swamp . 

13 

13 

0 

0 

6 

1922. 

Lincoln  (high  prairie) . 

26 

30 

2 

9 

JmJ 

Burlington . 

13 

18 

0 

10 

Low  prairie . 

25 

28 

3 

8 

Salt-flat . 

14 

14 

1 

1 

Swamp . 

14 

16 

.... 

4 

6 

ATTAINMENT  OF  OBJECTIVES. 

The  conclusion  seems  to  be  warranted  that  the  general  objective  of  de¬ 
veloping  the  basic  method  of  experimental  vegetation  so  that  it  combines  the 
maximum  of  demonstrability  and  objectivity  has  been  achieved.  While  the 
methods  involved  require  further  refinement  and  testing,  there  can  be  little 
question  that  they  are  prerequisite  to  fundamental  and  permanent  progress 
in  the  field  of  vegetation.  The  special  objectives  set  have  also  been  attained, 
though  necessarily  in  varying  degree,  since  such  problems  as  those  of  the  cycle 
and  of  competition  will  constantly  unfold  with  advancing  research.  Both 
planting  and  factor  results  have  confirmed  the  essential  variety  within  unity 
that  characterizes  the  grassland  formation  with  its  associations,  and  harmonize 
completely  with  the  evidence  from  cyclic  changes  and  relicts.  They  have 
further  illuminated  the  relation  of  serai  habitats  and  communities  to  those  of 
the  climax,  and  have  likewise  justified  the  concepts  of  subclimax,  postclimax, 
and  preclimax.  The  essentially  subclimax  nature  of  the  low  prairie  has  been 
corroborated,  as  have  also  the  climatic  and  phylogenetic  relationships  of  the 
subclimax  prairie.  The  evaluation  of  competition  as  a  controlling  process  in 


OBJECTIVES. 


153 


grassland  has  been  attended  by  unexpected  success,  especially  in  connection 
with  the  persistence  of  subclimax  prairie  in  regions  of  forest  climate.  With 
respect  to  natural  migration,  the  experimental  evidence  lends  no  support  to 
the  assumption  that  single  or  scattered  individuals  regularly  invade  climaxes 
with  success,  but  on  the  contrary  indicates  that  all  such  invasion  is  a  mass 
movement  in  response  to  wet  and  dry  phases  of  climatic  cycles.  The 
demonstration  of  the  phyletic  relationship  between  subclimax  prairie,  true 
prairie,  mixed  prairie,  and  short-grass  areas  and  between  the  corresponding 
climates  in  the  first  three  cases  appears  conclusive,  and  in  conjunction  with 
relict  and  cyclic  results  will  constitute  the  basis  for  future  research  in  the 
grassland  formation. 


154 


EXPERIMENTAL  VEGETATION. 


BIBLIOGRAPHY. 


Clements,  F.  E. 

1897.  Peculiar  zonal  formations  of  the  Great  Plains.  Am.  Nat.  31:968. 

1904.  Development  and  structure  of  vegetation.  Rep.  Bot.  Surv.  Nebr.  7. 

19042.  Formation  and  succession  herbaria.  Univ.  Nebr.  Studies  4:329. 

1905.  Research  methods  in  ecology. 

1907.  Plant  physiology  and  ecology. 

1916.  Plant  succession.  Carnegie  Inst.  Wash.  Pub.  242. 

1920.  Plant  indicators.  Ib.,  Pub.  290. 

1921.  Aeration  and  air-content.  Ib.,  Pub.  315. 

1922.  The  original  grassland  of  Mohave  and  Colorado  Deserts.  Carnegie  Inst. 

Wash.  Year  Book  21:350. 

The  method  and  principle  of  relicts.  Ib.,  351. 

Rainfall  and  climatic  cycles.  Ib. x  354. 

1923  The  original  vegetation  of  Death  Valley.  Ib.,  22: 

Application  of  the  relict  method.  Ib.,  317. 

Rainfall  and  climatic  cycles.  Ib.,  318. 

- and  E.  S.  Clements.  1921.  Changes  in  vegetation.  Ib.,  20:405.  1922 

Changes  in  grassland.  Ib.,  21:348,  22:316. 

- and  G.  W.  Goldsmith.  1921-23.  The  phytometer  method.  Ib.,  20-22. 

- .  1924.  The  phytometer  method  in  ecology. 

- and  H.  M.  Hall.  1919-23.  Experimental  taxonomy.  Ib.,  18-22. 

- and  D.  C.  Lutjeharms.  1921-22.  Slope-exposure  studies.  Ib.,  20-21. 

- and  J.  E.  Weaver.  1919-23.  Transplant  quadrats  and  areas.  Ib.,  18-23. 

Hall,  A.  D.  1920.  The  soil.  An  introduction  to  the  scientific  study  of  the  growth  of 
crops. 

Lutjeharms,  D.  C.  1924.  Environmental  differences  on  north  and  south  slopes  of  a 
canyon. 

Pool,  R.  J.  1914.  A  study  of  the  vegetation  of  the  sandhills  of  Nebraska.  Minn.  Bot. 
Studies  4: 189. 

Pound,  R.,  and  F.  E.  Clements. 

1898.  The  phytogeography  of  Nebraska. 

18982.  The  vegetation  regions  of  the  prairie  province.  Bot.  Gaz.  25:381. 

1900.  The  phytogeography  of  Nebraska.  Second  edition. 

Shantz,  H.  L. 

1906.  A  study  of  the  mesa  region  east  of  Pike’s  Peak:  the  Bouteloua  formation. 

Bot.  Gaz.  42:16. 

1911.  Natural  vegetation  as  an  indicator  of  the  capabilities  of  land  for  crop  produc¬ 
tion.  U.  S.  Dept.  Agr.,  Bur.  PI.  Ind.  Bull.  201. 

Weaver,  J.  E. 

1917.  A  study  of  the  vegetation  of  southeastern  Washington  and  adjacent  Idaho. 

Univ.  Nebr.  Studies  17:1. 

1919.  The  ecological  relations  of  roots.  Carnegie  Inst.  Wash.  Pub.  286. 

1920.  Root  development  in  the  grassland  formation.  Ib.,  292. 

1924.  Plant-production  as  a  measure  of  environment.  Jour.  Ecol.  12:205;  Carne¬ 
gie  Inst.  Wash.  Year  Book  22:312. 

- and  J.  W.  Crist.  1922.  Relation  of  hard-pan  to  root  penetration  in  the  Great 

Plains.  Ecology  3 : 237. 

- .  1924.  Direct  measurement  of  water-loss  from  vegetation  without 

disturbing  the  normal  structure  of  the  soil.  Ecology  5:153;  Carnegie 
Inst.  Wash.  Year  Book  22:312. 

- ,  F.  C.  Jean,  and  J.  W.  Crist.  1922.  Development  and  activities  of  roots  of  crop 

plants.  Carnegie  Inst.  Wash.  Pub.  316. 

- ,  Joseph  Kramer,  and  Maud  Reed.  1924.  Development  of  root  and  shoot 

of  winter  wheat  under  field  conditions.  Ecology  5:26-20. 

- and  A.  F.  Thiel.  1917.  Ecological  studies  in  the  tension  zone  between  prairie 

and  woodland.  Rep.  Bot.  Surv.  Nebr.  1917. 


BEHAVIOR  TABLES 


155 


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Table  58. — Sowing  in  denuded  quadrats ,  high  prairie ,  Lincoln,  Apr.  16  and  May  1920. — Continued. 


156 


EXPERIMENTAL  VEGETATION 


Table  59. — Sowing  in  denuded  quadrats,  Phillipsburg,  May  7,  1920. 


BEHAVIOR  TABLES 


157 


1  During  1922  Andropogon  nutans  grew  well  but  did  not  blossom,  while  in  1923  it  made  an  excellent  growth  and  flowered  abundantly. 


158  EXPERIMENTAL  VEGETATION. 


1.  Andropogon  nutans .  2  green  shoots  only,  15',  little  invasion .  2  small  clumps,  8-15',  will  blossom. 

9.  Liatris  punctata .  2  fine  stalks,  12',  thriving .  Now  16',  will  flower  abundantly. 

13.  Stipa  viridula .  Good,  many  well-tillered  clumps,  12-15' .  12-18',  thriving,  very  little  invasion. 


Table  61. — Seedlings  transplanted  to  high  prairie,  Lincoln,  May  11,  1921. 


BEHAVIOR  TABLES 


159 


Table  62. — Seedlings  transplanted  at  Phillipsburg,  May  19,  1921. 


160 


EXPERIMENTAL  VEGETATION 


Table  63. — Seedlings  transplanted  at  Burlington ,  May  20,  1921. 


BEHAVIOR  TABLES 


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EXPERIMENTAL  VEGETATION 


Table  65. — Sods  transplanted  at  Burlington ,  Apr.  15,  1921. 


BEHAVIOR  TABLES 


163 


Table  65. — Sods  transplanted  at  Burlington,  Apr.  15,  1921 — Continued. 


164 


EXPERIMENTAL  VEGETATION 


Table  66. — Sods  transplanted  to  gravel-knoll ,  Lincoln ,  Apr.  20,  1920. 


BEHAVIOR  TABLES 


165 


Table  66. — Sods  transplanted  to  gravel-knoll ,  Lincoln ,  Apr.  20,  1920 — Continued. 


166 


EXPERIMENTAL  VEGETATION 


Table  67. — Sods  transplanted  to  low  prairie ,  Lincoln,  Mar.  22  to  Apr.  24,  1920. 


BEHAVIOR  TABLES 


167 


Table  67. — Sods  transplanted  to  low  prairie ,  Lincoln ,  Mar.  22  to  Apr.  24,  1920 — Continued. 


168 


EXPERIMENTAL  VEGETATION 


Table  68. — Sods  transplanted  to  salt- flat,  Lincoln ,  Apr.  24-26,  1920. 


BEHAVIOR  TABLES 


1  Planted  here  in  1919. 


Table  68. — Sods  transplanted  to  salt-flat ,  Lincoln ,  Apr.  24~26,  1920 — Continued. 


170 


EXPERIMENTAL  VEGETATION 


BEHAVIOR  TABLES 


171 


1  Transplanted  into  the  Poa  zone. 


69. — Sods  trnnsplanted  to  swamp  and  Poa  zone,1  Lincoln,  Apr.  24,  1920 — Continued. 


172 


EXPERIMENTAL  VEGETATION 


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CLEMENTS  AND  WEAVER 


PLATE  1 


A.  — Detail  of  high  prairie,  showing  the  luxuriant  estival  society  and 

amount  of  forage  produced  in  June. 

B.  — General  view  of  high  prairie  at  Lincoln,  Nebraska. 


CLEMENTS  AND  WEAVER 


PLATE  2 


A.  — Mixed-prairie  station  at  Phillipsburg,  Kansas. 

B.  — Corner  of  short -grass  plains  station  at  Burlington,  Colorado. 


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CLEMENTS  AND  WEAVER 


PLATE  3 


penetration  4  and  2.7  feet  respectively. 


iifpvpfisrry  of  iujnois  tuuxinv 


CLEMENTS  AND  WEAVER 


PLATE  4 


Year-old  Elymus  canadensis  (A),  Bouteloua  racemosa  (B),  and  Andropogon  nutans  (C);  maximum  penetration  about  3,  c 

and  4  feet  respectively. 


CLEMENTS  AND  WEAVER 


PLATE  5 


A.  — Gravel-knoll  station,  Lincoln. 

B.  — Low-prairie  station,  Lincoln,  showing  transplanted  sods 


CLEMENTS  AND  WEAVER 


PLATE  6 


A.  — Low-prairie  station  in  September  showing  height  of  subclimax  dominants. 

B.  — Salt-flat  station.  Lincoln;  the  chief  grass  is  Distichlis  sp:cnta. 


4 


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[  CLEMENTS  AND  WEAVER 


PLATE  7 


A.  — View  of  sod  transplants  in  swamp  at  Lincoln,  showing  water  standing  on  surface. 

B.  — Subclimax  prairie  at  Nebraska  City,  showing  rank  growth  of  Stipci  spar  tea  and 

Ceanoth.us  ovatus  held  in  check  by  mowing. 


CLEMENTS  AND  WEAVER 


PLATE  8 


A. — A  single  season’s  growth  of  Andropoqon  nutans  from  block  of  sod  (left)  and  from  seed  fright)  on  low  prairie  at  Lincoln. 

B.  — Year-old  Bouteloua  hirsula  grown  on  high  prairie  at  Lincoln. 


CLEMENTS  AND  WEAVER 


PLATE  9 


Year-olcl  seedlings  of  Andropogon  scoparius  (right),  A.  nutans  (center),  and  A.  furcalus  (left)  « 
high  prairie;  plants  about  6  to  8  inches  tall. 

Root  system  of  year-old  Andropogon  furcatus  from  cultivated  lowland,  Lincoln;  scale  in  feet. 


CLEMENTS  AND  WEAVER 


PLATE  10 


A.  — Bulbilis  dactyloides  sod  in  high  prairie. 

B.  — Andropogon  nutans  in  September  of  first  season,  showing  marked  growth 

without  competition. 


CLEMENTS  AND  WEAVER 


PLATE  11 


A.  — Calamovilfa  longifolia  in  September  of  first  season,  grown  in  rich  silt-loam. 

B.  — Bouteloua  gracilis  one  year  old,  grown  in  cultivated  soil. 


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CLEMENTS  AND  WEAVER 


PLATE  12 


Roots  of  year-old  Muhlenbergia  pungens  (A)  and  Calamovilja  longifolia  (B)  grown 
in  rich  silt-loam;  depths  of  penetration  2.5  and  6  feet  respectively.  (C) 
Andropogon  halli  at  end  of  first  year  in  silt-loam. 


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CLEMENTS  AND  WEAVER 


PLATE  13 


Andro  pogon  nutans  planted  in  denuded  quadrats  at  Nebraska  City  (A)  in  1922,  (B)  in  1920. 

Photographed  June  3,  1922. 


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CLEMENTS  AND  WtAVER 


PLATE  15 


A.  — Sod-cores  and  details  of  installation,  Burlington. 

B.  — Clip-quadrat  in  Bulbilis-Bouieloua  short-grass,  Burlington. 


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